WO2020100155A1 - A hand held audiometer device and method thereof - Google Patents

Abstract

A hand held audiometer, comprising a power supply; a keyboard control unit including a keypad for input signals; a subject response controller including a push button component in order to provide input subject response; a sine wave generator configured for reference sine wave generation; an audio amplifier and attenuator configured to control the amplitude of the pure tone sine wave; a display control block for controlling a graphical display; a test selection mode configured for selection control for the air and bone conduction test; an air conduction means transmission of the pure tone audio signal to air conduction headphones; a bone conduction means for a bone vibrator and a microcontroller including audio peripherals i.e. microphone and audio DAC with speaker and their individual controls configured for controlling the pure tone wave generation with different frequencies and amplitudes and also to perform audiogram test.

Description

A HAND HELD AUDIOMETER DEVICE AND METHOD THEREOF

FIELD OF THE INVENTION

[001] The present invention relates to a hand held apparatus for checking the hearing capabilities of a person. More particularly, the present invention relates to a low cost architecture of Audiometer by use of differential pressure sensor and thin film structure with increased accuracy using DSP controllers.

BACKGROUND AND PRIOR ART [002] Problems: In 2012, WHO released new estimates on the magnitude of disabling hearing loss. The estimates are based on 42 population-based studies. Estimates are as follows:

[003] There are 360 million persons in the world with disabling hearing loss (5.3% of the world’s population). 328 million (91%) of these are adults (183 million males, 145 million females), 32 (9%) million of these are children.

[004] The prevalence of disabling hearing loss in children is greatest in South Asia, Asia Pacific and Sub-Saharan Africa. Approximately one-third of persons over 65 years are affected by disabling hearing loss.

[005] The numbers of subject are increasing day by day and there is an urgent need to address these problems. Early detection of the hearing loss can enable us to find suitable medical /surgical solutions to the hearing problem and thus reduce the adverse effects of hearing loss. The availability of audiometers or hearing test device is necessary in large scale. Various efforts have been made for making diagnostic audiometer for hearing test by various persons, firms and organizations. The major drawbacks of the available devices are:

[006] Type of audiometer available i.e. manual audiometer and automatic audiometer with drawbacks mainly:

• Complex design requiring a skilled professional to operate it. • Higher cost of the Device which results in non-availability of the device to the smaller centres especially in rural/semirural areas.

In general, the portability is an issue. Even the ones which are portable are quite expensive.

[007] Known audiometers are of two main types: Manual & Automatic.

[008] In the manual system and method of audiometer testing, a skilled operator adjusts and controls the audiometer system, thereby sending different types of audio signals either through earphones, loudspeakers or bone vibrators, to a subject who is commonly sitting in a quiet room (sound treated). The subject is requested to provide a response whenever he/she hears the sound on the test ear, either by activating a switch connected to a pilot light, or by raising his hand or by any other visible or audible means. The audiologist or the operator looks for the response of the subject. The procedure is followed for all the frequencies and responses are noted down as thresholds of hearing.

[009] In the automatic method known as the Bekesy method of auditory testing, the audiometer presents to the subject automatically changing tone frequencies while the intensity of the signal is controlled by the subject by means of a push button switch activating a motor controlling the motion of an intensity attenuator. The subject responses are also automatically recorded by means of a writing pen moving over a chart as the test progresses. While the Bekesy method is considered by those skilled in the art of audiology as a major advance, it still requires the presence of a skilled operator and the use of rather sophisticated mechanical systems [US Patent 4,107,465]

[0010] An improved computerized audiometer for testing the hearing of one or more of a variable number 40 of people at the same time and generating programming for a programmable hearing aid is provided [US Patent 4,489,610] The audiometer includes at least one head set and control switch for use by the person being tested, a tone generator for applying a selected sequence of tones of varying frequency and amplification to the head set under the control of a central processing unit, a memory for storing the results of the test for analysis by the central processing unit, and output means adapted to program a hearing aid in accordance with the results of said analysis when coupled thereto. The tone generator may be adjustable to reflect the results of such feedback. The audiometer may be under the control of an operator provided with a display and keyboard coupled to the central processing unit. Local and remote printers, data storage and modem devices may be provided [US Patent 4,489,610] This system is having a number of features which are required in audiometric devices but the device is too much bulky and not easy to operate.

[0011] A combination otoscope and audiometer provided with conventional lighting means and an unobstructed viewing passage for visually inspecting the ear canal of a subject. The hand held instrument is also provided with a calibrated electronic circuit that automatically produces a sequence of tones of different frequencies and intensities, together with means for transmitting these tones to the subject ear. The circuit includes timing means for precisely controlling the duration of each tone. Neither the production of the tones nor the duration thereof is under the control of the operator. The exterior of the instrument is provided with indicators in the form of light emitting diodes to tell the operator when each tone is being transmitted to the subject ear [U.S. Patent No. 4,567,881] The device is good for initial inspection of the ear canal and ear screening. It will not provide complete audiometer functions as required. In [U.S. patent no. 3,882,848] a test probe for impedance audiometer is discussed which is used for hearing loss.

[0012] A hearing testing method permits the testing of infants and others who cannot respond and provides an accurate and rapid test for others. A group of pure tones at selected amplitudes and frequencies is played, through earphones, to a subject. Electrodes connected to the subject head detect the subject brainwaves which are evoked responses to those tones. The brain waves are amplified, averaged according to the tone frequencies, automatically analysed on a statistical basis using the’t’ test, and used to display a profile of the subject hearing ability [U.S. Patent No. 3,799,146] The device is based on the response coverage from the brain waves. The accuracy depends on the signal generated by the nerve system on playing of pure tones on the ear. Most of the time it is difficult to understand the brainwaves that it is actually coming due to hearing or any other things. [0013] An evoked response audiometer is disclosed in which the subject is presented with a continuous auditory signal which is amplitude modulated and the evoked brain potentials of the patient (EEG) are recorded. The potentials are amplified and filtered and are averaged over a number of sampling periods to improve the signal to the noise ratio. The averaged signals are then analysed to determine the amplitude and phase of the main components of the response to determine whether phase locking has occurred. The phase of the main components is then plotted against variation of the modulating frequency and the gradient of the plot provides the latency of the response from which neurological and other factors of significance to the hearing of the subject may be determined. The sound pressure level of the auditory signal is also varied and the amplitude and phase of the response plotted against these changes to provide an indication of the sensitivity of the hearing of the subject [US Patent No 4,462,411] The device is similar to the above device where the brainwaves are analysed to get the response of the subject. Again it can be said that the response may be false because of the unknown nature of the signals generated in the brain. One can falsely detect the signal and correlate with the audiometric function and the result may vary.

There exists in industry a need to have equipment which allows a rapid test of hearing. Such a requirement is not easily possible to fulfil with instruments of prior art which usually have to be installed in quiet rooms away from the work premises.

[0014] The decibel level perceived depends on the subject seating position and changes of head position. Furthermore, recorded sound disks are subject to significant amounts of wear, imparting extraneous noise onto the test rendering the hearing test less and less accurate as the recorded material ages. While the prior art has taught various means for the simultaneous testing of a plural number of individuals at a test center, it has not suggested the use of distantly remote testing centers communicating by telephone line or other long distance link with a central data processing center. In addition, testing centers utilizing the multiphasic concept of administering a variety of tests to a plural number of individuals situated in individual soundproof booths or other noise excluding means, have been characterized by excessively high costs of fabrication due to the necessary soundproofing of the test instruments away from the test booths. These rooms of soundproof construction have, on the average, cost around seven thousand rupees per square foot [U.S. patent no. 3,808,354]

[0015] A further method of auditory testing has been proposed in which a computer is used to present the tones to the subject in a programmed sequence and record his responses. Reference is made to U.S. Pat. No. 3,809,811 and Canadian patent 950,106. In this type of instrument, the triggering of different intensities and frequencies by the programming circuit is entirely dependent upon the feedback from the subject responses, through his actuation of a“YES” button, but calling for a relatively complex electronic circuitry.

[0016] An interface for providing an appropriate dynamic range for audiometric testing comprising:

[0017] A digital wireless interface supported by a base unit and a remote unit wherein the base unit receives a signal comprising test sound information from an audiometer and provides the signal as digitally encoded test sound information to the remote unit via the digital wireless interface, wherein the amplitude of the signal provided via the wireless interface is automatically scaled based on a comparison of an average amplitude of the signal to preset thresholds [EP 2316 337 Al, 2011] This device operates over wireless control. The architecture of the device is bulky in nature and cannot be taken out easily. The wireless controls for this type of sensitive testing may not be appropriate.

[0018] An audiometer with interchangeable transducer of sound is proposed in [US 2009/0090165 Al] Here the microcontroller unit detects or the user can provide the transducer details with the keypad. The microcontroller saves the calibration factor in the EEPROM. This data is loaded after the sensing or from command level of the type of transducer. This system is very complex in architecture and cannot be handled without an audiologist.

A home hearing test for use with a conventional home audio system comprising an audio player and a set of headphones connected to the audio player. The home hearing test includes an audio medium such as a compact disc playable in the audio player and containing a calibration tone recorded at a predetermined decibel level and a number of pre-recorded sequences of tones. Each sequence has tones recorded at different decibel levels and decreasing by a step value. The home hearing system includes a calibration device for calibrating the output of the audio system to the ears of a person wearing the headphones against the predetermined decibel level of the calibration tone [US Patent 5,928,160] The audio range provided by the device for audiometer testing is very limited and the functions available are very less.

[0019] In view of the scenario the requirement of low cost and handy device is much more prominent. The uses of audiometers are required in large geographical areas but due to the costing, complex operating procedure and portability it is not possible to reach the desired level. The invention which we are providing is a low cost, light weighted handy device which is easy to operate.

[0020] Advantages and disadvantages:

[0021] The device is to perform hearing test or audiometry and a method for identifying

[0022] Nature/ type of hearing

[0023] Degree of hearing loss

[0024] Probable cause of hearing impairment.

[0025] According to the WHO hearing loss is prevalent disease in current situation. Early age detection and preventive steps can cure the problems before it gets worsened. The availability of test centres for the hearing test is very limited. As the technology have grown various audiometric system have come up for performing hearing test.

[0026] The available devices have a number of limitations which require advancement for better performance, easy operability and handy use.

[0027] DISADVANTAGES

[0028] Complex Operability: There are various audiometric systems available in the market based on different methods for measurement like ear screening for thresholds, complete hearing test, air conduction only and bone conduction test device. The handling and operability of the instrument becomes very difficult in this case. As the complexity increases the knowledge level required to operate the device is also more. A trained professional / audiologist only can perform the hearing test with the device. The invented device will provide the required function with less complexity. Little knowledge and training on the device to an educated person can enable to equip the person for performing the hearing test.

[0029] Heavy weight: The available audiometer systems used for the audiometry are bigger in size hence the weight of the system is more. The size of the system also depends on the architecture or principle used for the audiometer design and development. It becomes difficult to handle the equipment for easy operability. The mobility of the system will affect the use also. A device which comes in small size can be picked up in a small bag and taken to the subject home at interior places or when the subject is very old or infirm or any other place for use such as screening camps in rural areas/schools. The weight also increases as the number of facilities in the system increase like large display system, number of keypads for operability etc. So to reduce the weight by making the system compact is required without reducing various functionalities.

[0030] Higher Cost: The Audiometer systems which are available in the market are bulky and costly. There are models which are cheaper but they have very less features. A good Audiometers is the one which provides a rapid result or real time results, graphical displays showing the input and output waveforms like differential pressure curve, expiration volume time curve and flow volume loop. These features are very necessary for the medical professional to understand the typical conditions of the subject. In the medical field it is prominent that the cost of the device decides the reach of the device to common man. Hence it is a major requirement to bring the cost down so that more number of people can get diagnosed easily.

OBJECT OF THE INVENTION

[0031] Accordingly, the primary object of the invention is to reduce the complex architecture of Audiometer by using differential pressure sensor and thin film structure. [0032] Another object of the invention is to provide a hand held Audiometer which is light weighted and easy to operate.

[0033] Another object of the invention is to provide a hand held Audiometer at a lower cost with high accuracy using DSP controllers.

[0034] How the foregoing objects are achieved will be clear from the following description. In this context it is clarified that the description provided is non-limiting and is only by way of explanation.

SUMMARY OF THE INVENTION

[0035] Hearing is important. It is the sensory channel by which we are connected to other people, warned of impending dangers, and entertained by music and laughter. Good hearing enables us to perceive the laughter of friends, the cries of a baby, and the breeze rustling through the trees. Without it, we feel isolated from the world round us, and frustrated by our inability to fully understand the flurry of activity that surrounds us. Man is a social creature, and hearing is critical to his ability to function as such.

[0036] Audiometry is performed to check the status of an individual’s hearing and identify the type and amount/ degree of hearing loss if any. The conditions mentioned below may cause hearing impairment.

• Being around loud noises often at work for long durations

• Mowing the lawn or using power tools as a regular job

• Shooting guns or other weapons

• Loud music, both live and recorded

• Too much ear wax

• Getting hit on the head

• Having a chronic ear infection

• Taking certain ototoxic drugs

• Aging effect and nerve degradation

• Hereditary hearing loss [0037] Depending on the part of the ear involved, there could be middle/ inner ear problems. Audio-logical investigations help us to diagnose the nature of deafness and localize the site of disorder. The method by which subject hearing sensitivity can be determined is termed as audiometry.

[0038] In this technique, auditory stimuli with varying intensity levels are presented to the person who responds to these stimuli. The minimum intensity level of these stimuli to which consistent responses are obtained is taken as the threshold of hearing. Depending on this threshold, the subject hearing sensitivity can be estimated by obtaining an audiogram. An audiogram is a plot of threshold intensity versus frequency. Then the best- suited medical/ surgical treatment or hearing aid / assistive devices can be prescribed.

[0039] In brief this is a device to perform hearing test and helps identifying

Nature/ type of hearing loss

Degree of hearing loss

Probable cause of hearing impairment.

[0040] This disclosure aims to provide a hand held light weight device for performing the hearing test at an affordable price.

[0041] Therefore such as herein described a hand held audiometer for detecting a hearing loss of a person, comprising a power supply; a keyboard control unit including a keypad for input signals; a subject response controller including a push button component in order to provide input subject response; a sine wave generator configured for reference sine wave generation; an audio amplifier and attenuator configured to control the amplitude of the pure tone sine wave; a display control block for controlling a graphical display; a test selection mode configured for selection control for the air and bone conduction test; an air conduction means transmission of the pure tone audio signal to air conduction headphones; a bone conduction means for a bone vibrator and a microcontroller including audio peripherals i.e. microphone and audio DAC with speaker and their individual controls configured for controlling the pure tone wave generation with different frequencies and amplitudes and also to perform audiogram test. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0042] The nature and scope of the present invention will be better understood from the accompanying drawings, which are by way of illustration of a preferred embodiment and not by way of any sort of limitation. In the accompanying drawings:

[0043] Figure 1 illustrates a Block Diagram of audiometer in accordance with the present invention;

[0044] Figure 2 illustrates an Audiogram for the test (AC) in accordance with the present invention;

[0045] Figure 3 illustrates an Audiogram for the test (BC) in accordance with the present invention;

[0046] Figure 4 illustrates an Experimental circuit arrangement for Signal generation & Audiogram in accordance with the present invention;

[0047] Figure 5 illustrates a Flow Chart of the Working of presented audiometer in accordance with the present invention;

[0048] Figure 6 illustrates an Audiogram Framework in accordance with the present invention;

[0049] Figure 7 illustrates a 4x4 Matrix keypad Layout in accordance with the present invention;

[0050] Figure 8 illustrates a Front Panel of the Audiometer Device in accordance with the present invention;

[0051] Figure 12 is a photographic representation of a Complete Audiometer in accordance with the present invention

DETAILED DESCRIPTION OF THE INVENTION [0052] Audiometer and Hearing Test: Audiometer is used to measure the ability of a subject to hear at specific frequencies. Fundamental to this measurement is pure tone measurement. The audiometer is used to generate pure tone signals at specific frequencies within the 250 Hz to 8 kHz range. For each frequency the level of loudness is incremented from soft to loud. The subject is asked at which point he/she starts to hear the sound, which will then represent the subject hearing threshold at that frequency. The final result is plotted as an audiogram that will be interpreted by medical professionals to determine proper treatments.

[0053] In all Human hearing ranges from 20 Hz to 20 kHz. There is little speech information above 8000 Hz. Perception of frequencies below 100 Hz is increasingly tactile in nature, making them difficult to assess. In general the audiologists test only in the range of 250-8000 Hz, often in octave steps. Standardized frequencies tested include 250, 500, 1000, 2000, 4000 and 8000 Hz. This represents octave intervals, by convention, but intervening frequencies may also be tested.

[0054] In acoustic measurements, sound level is often given in dB, taking sound pressure of 20 Pa as the reference level, and is known as sound pressure level (SPL).

Sound level in dB SPL = 20 log (measured sound pressure / 20 Pa). However, in audiometry the sound level of pure tones is given in dB by taking average hearing threshold of normal hearing young adults as the reference, and is known as hearing level (HL). [0055] Sound level in dB HL = 20 log (measured sound / average threshold of normal hearing)

[0056] The hearing threshold is frequency dependent. Hence, SPL corresponding to a given HL varies with frequency. Intensity levels in audiometers are indicated in HL. Table 1 gives the dB SPL (dB HL) threshold values of a normal person for standard frequencies. The "0 dB" hearing level in audiometry is a modal value derived from a large population of normal persons. Normal values for auditory thresholds were defined by the International Standards Organization (ISO) in 1984. These values are derived from large population studies of normal adults 18-30 years of age. The following table gives the dB SPL values corresponding to 0 dB HL for standard frequencies.

[0057] Threshold values in dB SPL for 0 dB HL (ISO, 1984).

Frequency (Hz) 250 500 lk 1.5k 2k 3k 4k 6k 8k

dB SPL 25.5 11.5 7 6.5 9 10 9 10.5 13

[0058] Since both HL and SPL are logarithmic units, a certain increment in HL corresponds to the same value increment in SPL.

[0059] An audiogram is a plot of threshold intensity versus frequency. The intensity scale in HL increases downwards, and hence the audiogram resembles like an attenuation response, a lower point on the audiogram indicating higher loss. A typical audiogram (dB HL vs. frequency graph) comparing normal and impaired hearing is shown in Fig.3. The dip or notch at 4 kHz, or at 6 kHz signifies noise-induced hearing loss.

[0060] Most thresholds are approximately 0 dB HL for a normal ear. Points below 0 dB

HL denote louder threshold levels. Those above 0 dB HL are expressed in negative decibels and are less intense. An audiogram comprises of four separate curves. They are right ear air conduction (AC), right ear bone conduction (BC), left ear AC, and left ear BC. The symbols used on most audiograms are X - left air conduction, O - right air conduction.

Technical Details

[0061] At present, there are various types of audiometers readily available in the market. They can be different depending on the specifications and features, but generally a dedicated hardware is needed for high-quality and reliable measurements, resulting in high price. In terms of research, historically the earlier work focused on hardware implementation, usually at the integrated circuit (IC) or embedded system levels. Techniques such as direct digital synthesis (DDS) have been considered. As the availability of good-quality personal computer expanded, the focus has shifted towards PC-based systems. Some have also attempted on integrating other hearing loss measurement features into the same device. Finally, remote hearing scanning and active noise control based on PC has been introduced.

[0062] The objective of the invention is to develop a low cost hand held audiometer device which will work in conjugation with the hearing aid. The audiometer will use the audio capability of the hearing aid to generate pure tone sine wave and perform hearing test. This will reduce the hardware requirement for dedicated audiometer setup and PC etc. The audiometer device is having a 2.4” TFT screen for displaying the audiometer setup, control and audiogram. The device is having a 3*4 matrix keypad to provide the control facility for hearing test. A response switch is provided to collect the subject hearing response.

Details of the Device

[0063] The block diagram of the architecture of the device is shown in fig 1. The overall components of the complete device are divided in various blocks. These are:

a. Power supply

b. Power control

c. Keyboard control

d. Subject response controller

e. Sine wave generator

f. Noise generator

g. Audio amplifier and attenuator

h. Display control

i. Graphical display

j. Test selection

k. Air conduction

l. Bone conduction

m. Microcontroller [0064] The power supply is to provide the power to the device. It may be a battery connection, power bank, USB connection from the PC etc. The input required is 5V supply. Power control section controls the different peripherals connected to the systems like graphical display, keyboard, subject response circuitry, audio amplifier and attenuation circuitry etc.

[0065] The keyboard control includes the keypad input buttons which is used for the audiometer control. It enables the user to control the audiometer functions for hearing test. The input selection includes start of test, selection of amplitude, frequency, air conduction test, bone conduction test, right and left channels, data locking and print etc.

[0066] The subject response controller is a circuitry which is having a push button component used for the indication of the subject response while listening to the pure tone. When the user press the switch the LED light connected to the subject response controller get ON’ and when the switch is released the LED OFF’ condition occurs.

[0067] Sine wave generator is responsible for the reference sine wave generation. This will be sent for the pure tone with selected amplitude and frequency. Similarly the noise generator circuit will generate the noise if required. [0068] Audio amplifier and attenuator control the amplitude of the pure tone sine wave.

This will generate the audio signals and send it to the headphone connected with the audiometer. The amplitude level is selected by the user or audiologist who is performing the test. [0069] Display control block controls the display device i.e. graphical display present in the audiometer. The graphical display is used to display the various control commands and the audiogram. [0070] Test selection is a selection control for the air and bone conduction test. This works as a switch between the air conduction and the bone conduction. The selection is made by the audiologist or the user. [0071] Air conduction means transmission of the pure tone audio signal to air conduction headphones.

[0072] Similarly the bone conduction is taken care of by bone vibrator.

SD Card Interfacing: [0073] The present hand held audiometer is equipped with SD card module which stores the tested data in text file (.txt). Once the testing for air conduction (AC) and bone conduction (BC) for both the ear are performed, the amplitude points are generated on screen simultaneously. The audiogram is generated and displayed on TFT screen when one presses the‘print’ button; the audiogram data for AC and BC are saved in the SD card attached with the audiometer. The audiogram of every test is appended in the same text file.

Power ON/OFF:

[0074] The audiometer is battery operated. The hand held device is useful for portability. The device can be taken out for hearing test very easily. It can be used with the external power source like USB adapter, Mobile charger etc., and simultaneously with the internal battery power. The on/off switch is provided so as to switch on/off the audiometer when required.

[0075] Microcontroller is the main component of the whole assembly. The microcontroller controls the above activity. All the programming is done onto the microcontroller. The communication to display in the graphic control, audio control, amplitude control etc. is sent by microcontroller. The features of the microcontroller are listed in the below sections. Similarly the various features of audio control are also discussed in the sections below.

[0076] The complete block diagram of the setup is shown in the figure no 1.

Procedure to Perform Hearing Test

Air Conduction (AC)

[0077] The head phones are placed over the subject ears. The right channel to right ear and the left channel to left ear of the subject. There is one switch in subject hand, so that if he is able to hear a particular level of sound then he/she will press the switch to indicate the response.

[0078] The Pure-tones are presented to one ear at a time. The other ear will be isolated from the test ear. The test will be done between 250Hz to 8kHz range of audio frequency. Whenever subject will hear the beep sound, he will eventually press the switch. That will indicate on the audiometer device by blinking of LED. So, the user or the audiologist will set that point for respective value of amplitude and frequency.

[0079] In this way doctor, will check the listening amplitude with respective frequency, and plot the curve called audiogram shown in figure 2. Now the doctor will take the average of thresholds obtained between 500-2KHz (Some cases 500-4KHz) because this is the most sensitive frequency range for human ear as far as the speech perception is concerned. Same test will be performed for other ear.

[0080] The‘X’ for left ear in blue color and Ό’ for right ear in red color is marked against the threshold levels of the subject. If there is a difference of more than 40dB in two ears, the better ear is masked to rule out its participation and the masked thresholds across the frequency range are obtained for the poorer ear.

[0081] If there is a hearing loss, bone conduction thresholds are obtained to ascertain the type of hearing loss v.i.z., conductive, mixed or sensori-neural. Bone Conduction 1BQ

[0082] In this bone-conduction testing, instead of using an earphone, an electromechanical vibrator is placed on the skull (mastoid process). Now repeat the same procedure as we did previously, and plot the thresholds for right and left ear as the case may be. The display for bone conduction in audiogram is‘>’ for left ear and‘<’ for right ear is used. The bone conduction is tested for 250 Hz- 4 kHz with the amplitude levels of OdBHL- 65dBHL.

Experimental Setup of Developed Audiometer

[0083] The microcontrollers used for the audiometers are based on an atmel atmega256. It has 54 digital input/output pins (of which 15 can be used as PWM outputs), 16 analog inputs, 4 UARTs (hardware serial ports), a 16 MHz crystal oscillator. It contains everything needed to support the complete system.

Another microcontroller used for the audio control is STM32F4.

[0084] This board is equipped with audio peripherals i.e. microphone and audio DAC with speaker. All the audio related works are performed in this. Pure tone wave generation with different frequencies and amplitudes are covered in this. The communication from Atmel microcontroller for different instructions to perform audiogram test is implemented in it.

Audio DAC CS43L22

[0085] 12, 24, and 27 MHz Master Clock Support in Addition to Typical Audio Clock Rates

High Performance 24-bit Converters

• Multi-bit Delta-Sigma Architecture

• Very Low 64Fs Oversampling Clock Reduces Power Consumption

• Low Power Operation

• Stereo Analog Pass-through: 10 mW @ 1.8 V

• Stereo Playback: 14 mW @ 1.8 V

90% efficiency at 800mW

Full digital control with I2S interface

Soft ramp increase and decrease in volume control

Experimental Setup for Audiogram

[0086] Figure 4 shows the experimental setup of the audiogram development. It consist of microcontroller development board, amplifier stage, interrupt switch for user response and earphone of 10 ohm impedance and 108±4dB /mW sensitivity.

Figure 5 illustrates the flow chart of the functioning of the audiometer programming. Audiogram Display Framework

[0087] The audiometer display is shown in the figure 6. Here we can see that the status of the selected pure tone can be seen. i.e. air conduction/ bone conduction, right/ left channel, amplitude levels in dBHL, frequency component being played, tone on/off signal and finally audiogram. This will help the user/ audiologist to recognize the state of the audiometer and can control accordingly.

[0088] The manual mode of operation is implemented with the help of 4x4 keypad. The figure 7 displays a logical implementation of various functions on keypad.

[0089] The device performs different task according to the key pressed. Various factions of the key are described below:

Start: Start of test. Generate 250Hz pure tone with OdBHL amplitude.

Amp+: Increase the amplitude level +5dBHL Clr: Clear the Screen

Freq-: Changeover of frequency from higher to lower Reload: Reload the previous results

Freq+: Changeover of frequency from lower to higher ACL: Air Conduction Left Ear Selection ACR: Air Conduction Right Ear Selection BCL: Bone Conduction Left Ear Selection

BCR: Bone Conduction Right Ear Selection Amp-: Reduce the amplitude gain -5dBHL

Lock: Store the current frequency component amplitude level and plot it in the audiogram Print: Print the audiogram in the TFT display

[0090] Simple operating steps

Step 1 : Make connections of board. Connect to power supply. Plug the headphone and subject response switch.

Step 2: Place the headphone to ear of the subject. Instruct the Subject. Inform about switches to subject. Start with 1000Hz at 40dBHL right ear if there is no better ear. The sequence should be 1000, 2000, 4000, 8000 and recheck at 1000, 500, 250 Hz respectively.

Step 3: Power ON the switch and press start button of keypad. The air conduction sound on 250Hz at OdBHL will start to play on right ear when the user/ audiologist press the ON button.

Step 4: Ask the subject if he is able to hear the tone and give response by pressing the switch once start to listen the tone. Step 5: If there is no response from the subject then press the Amp+ switch to increase the amplitude level and check for the subject response.

Step 6: Repeat the process till the subject is able to hear the signal/tone.

Step 7: Once the response is obtain then again check the hearing level by pressing the Amp- key to confirm the hearing level.

Step 8: If the audiologist is satisfied with the subject response then lock the data by pressing Lock key. The data will be recorded and plotted over TFT.

Step 9: Now press the Freq+ to change the frequency and shift to the other frequency and again repeat the above process. Step 10: Once all the frequency data is collected then ask the subject to put earphone on left ear. And press the ACL key on keypad.

Step 11 : Now again perform the above steps for the left ear hearing levels. Once all the frequency data are recorded change the headphone and put the bone conduction vibrator. Step 12: Similarly perform the above test as per the recommendation and lock the thresholds levels for different frequency and ear.

Step 13: After the completion of the test press the print button to generate the audiogram image in the TFT display.

[0091] The test can be performed as per the requirement of the user/ audiologist. The sequence of testing etc. is on manual control.

[0092] The final output the invention is a low cost, handheld audiometer. The invented audiometer will provide the rapid result of hearing test thresholds level of air conduction and bone conduction. The invented device shows the result on the color graphical display.

The generated audiogram is shown with the required symbols. [0093] The severity in terms of nerve degradation and types of the diseased can be recognized by the device. The device is easy to handle and operate. The structure and functionality is very simple and can be operated by a person having education up to high school after basic training.

[0094] The cabinet is made in such a way that it can be handled and made portable easily. The local battery setup is provided to power the audiometer standalone. It can also be connected to power bank, Personal Computers and power adapter.

[0095] Figures 8 and 9 shows the front panel of the audiometer and complete audiometer system.

[0096] Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. It will be apparent to those having ordinary skill in the art that a number of changes, modifications, variations, or alterations to the invention as described herein may be made, none of which depart from the spirit or scope of the present invention. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims

We claim:

1. A hand held audiometer, comprising:

a) a power supply;

b) a keyboard control unit including a keypad for input signals;

c) a subject response controller including a push button component in order to provide input subject response;

d) a sine wave generator configured for reference sine wave generation;

e) an audio amplifier and attenuator configured to control the amplitude of the pure tone sine wave;

f) a display control block for controlling a graphical display;

g) a test selection mode configured for selection control for the air and bone conduction test; h) an air conduction means transmission of the pure tone audio signal to air conduction headphones;

i) a bone conduction means for a bone vibrator and

j) a microcontroller including audio peripherals i.e. microphone and audio DAC with speaker and their individual controls configured for controlling the pure tone wave generation with different frequencies and amplitudes and also to perform audiogram test.

2. The hand held audiometer as claimed in claim 1, wherein the power supply is configured to provide regulated power controlled via an ON-OFF switch including at least one from a battery connection, power bank, USB connection from the PC and delivers power to a plurality of connected peripherals at least from graphical display, keyboard, subject response circuitry, audio amplifier and attenuation circuitry etc.

3. The hand held audiometer as claimed in claim 1, wherein the keyboard control unit is configured for control of the audiometer functions for hearing test; and wherein the input selection includes start of test, selection of amplitude, frequency, air conduction test, bone conduction test, right and left channels, data locking and print etc.

4. The hand held audiometer as claimed in claim 1, wherein the push button component is used for the indication of the subject response while listening to the pure tone.

5. The hand held audiometer as claimed in claim 1, wherein the said sine wave signal is sent for the pure tone with selected amplitude and frequency.

6. The hand held audiometer as claimed in claim 1, wherein the amplitude level for the audio amplifier and attenuator is selected by the user or audiologist who is performing the test.

7. The hand held audiometer as claimed in claim 1, wherein the graphical display is configured to display the various control commands and the audiogram.

8. The hand held audiometer as claimed in claim 1, wherein the microcontroller used for the audio control is STM32F4 and audio DAC is CS43L22.

9. The hand held audiometer as claimed in claim 1, wherein the air conduction test includes Air Conduction (AC) placing of head phones over the subject ears with right channel to right ear and the left channel to left ear of the subject and pure-tones are presented to one ear at a time between 250Hz to 8kHz range of audio frequency.

10. The hand held audiometer as claimed in claim 1, wherein the bone- conduction test includes placing an electromechanical vibrator on the skull (mastoid process) and pure-tones are presented.

11. The hand held audiometer as claimed in claim 9, wherein the bone conduction is tested for 250 Hz- 4 kHz with the amplitude levels of OdBHL- 65dBHL.

12. The hand held audiometer as claimed in claim 1, wherein the said audiometer further includes memory SD Card Interfacing configured for storing and retrieving of the tested data in text file (.txt)

13. A method for carrying out an audiometry test with a hand held audiometer device as claimed in any of the preceding claims.