WO2008139404A1

WO2008139404A1 - An audiometer

Info

Publication number: WO2008139404A1
Application number: PCT/IB2008/051858
Authority: WO
Inventors: Hendrik Lambert Koekemoer
Original assignee: Hendrik Lambert Koekemoer
Priority date: 2007-05-09
Filing date: 2008-05-09
Publication date: 2008-11-20
Also published as: WO2008139404A8; GB0708944D0

Abstract

The invention relates to an audiometer (100) and to a method of conducting audiometry. The audiometer (100) includes at least one circum-aural earphone (102) for positioning over an ear of a patient, the circum-aural earphone (102) including a microphone (202) directed outwardly for receiving external or ambient sound, and an acoustic speaker (238) directed inwardly. The audiometer (100) also includes at least one inner earphone (104) operatively arranged within the circum-aural earphone (102), the inner earphone (104) including an in ear piece (106) for positioning in the ear, a microphone (230) directed outwardly, and an acoustic speaker (220, 221 ) directed operatively inwardly. The audiometer (100) further includes a control module configured to perform a first phase of active noise reduction and a second phase of active noise reduction and to emit a hearing-test sound via the speaker (220, 221 ) of the inner earphone (104).

Description

AN AUDIOMETER

FIELD OF THE INVENTION

This invention relates to an audiometer, which is a device or instrument for gauging and recording acuity of hearing. In particular, the invention relates to an audiometer that does not need be used in a sound booth even in noisy environments that is capable of performing standard audiological tests.

BACKGROUND OF THE INVENTION In traditional audiometry, patient or the test subject is situated in a soundproof booth that enables an audiologist to perform tests without the interruption of ambient noise. However, the use of a soundproof booth is not always plausible, especially in developing countries where resources and equipment are very limited.

The audiometer typically consists of either supra-aural (on ear), circum-aural

(over ear) or insert (in ear) earphones, together with other necessary hardware, capable of delivering sounds of varying frequency and volume (hearing level) to years of the patient. By monitoring the response (or lack of response) of the patient, the hearing threshold level of the test subject can be determined.

Different types of hearing loss could be present, e.g. conductive hearing loss, sensorineural hearing loss, mixed hearing loss (a combination of conductive and sensorineural), pseudohypoacusis, central auditory disorders and auditory neuropathy. To assess whether or not these types of hearing losses are present and to what extent they are present, different types of hearing tests have to be done.

The different types of tests that can be done include pure-tone air conduction audiometry, in which a sinusoid signal of a specific frequency is played into the test subject's ear at varying volume or sound pressure levels. The test subject is then asked to respond immediately when the sound is perceived. The sound pressure level is varied for a tone of a specific frequency until a threshold is reached where the test subject can just barely hear the presented signal. This is determined the hearing threshold for a tone of a specific frequency. A plot is made of the hearing thresholds for different frequencies ranging from 125 Hz to 20000 Hz. This plot is known as an audiogram.

The same type of testing can be done with the use of a bone vibrator situated on either the forehead of the test subject or on one mastoid of the test subject. This type of testing is known as pure-tone bone conduction testing and tests whether conductive hearing loss is present or not. Pure sinusoidal tones varying in frequency from 250 Hz to 8000 Hz are played at varying volumes or levels to assess the hearing loss of a test subject. Just as in the case of the audiogram, the different hearing thresholds are plotted versus frequency and the result is part of the audiogram.

Tympanometry may reveal any of the following: fluid in the middle ear, perforated ear drum, impacted ear wax, scarring of the tympanic membrane, lack of contact between the conduction bones of the middle ear, a tumour in the middle ear and more.

Tympanometry testing is used to assess the admittance of the ear canal, in other words, the ease with which energy flows into the ear canal (conceptually, the inverse of resistance). Tympanometry is used in diagnosing diseases of the middle ear. During tympanometry, the pressure inside the ear is varied typically between -400 daPa and +200 daPa relative to atmospheric pressure. A constant sound of 226 Hz is typically played into the ear and the reflection of this sound, as the pressure varies, is measured and plotted on a graph. This graph is known as a tympanogram.

Distortion product otoacoustic emissions (DPOAE) are sound-recordable responses generated when the cochlea is stimulated simultaneously by two pure tone frequencies whose ratio is between 1 .1 to 1 .3.

Other tests that can also be done are auditory evoked potential type of testing, specifically auditory brain stem response (ABR) and auditory steady-state response (ASSR) testing.

Auditory brain stem response (ABR) tests are used to assess the hearing of infants since infants cannot be tested in conventional ways. Other persons that cannot normally respond to traditional audiological tests, such as autistic individuals, dθvelopmentally delayed children, multiply handicapped children and persons suspected of pseudohypoacusis can also benefit from these tests.

Auditory evoked potentials are electrical potentials that are recorded from the scalp and face of the test subject and are electrical potentials that are evoked by auditory stimulation. Typically, click or tone-burst stimuli are used to evoke the potentials. Click stimuli are brief rectangular pulses of typically 50 - 200 μs duration with an instantaneous onset. The rapid onset of the click provides good neural synchrony, thereby eliciting a clearly defined ABR. The short-duration tone burst (or tone pip) gives a better indication of frequency-specific ABR. These stimuli are brief tones with rise/fall times of only a few milliseconds (< 5 ms) and have brief or no plateau duration. These stimuli still have considerable spectral splatter but it can be reduced by windowing the stimuli.

ABR is also used to assess auditory sensitivity and to detect lesions along the auditory nerve and brain stem pathways (otoneurological assessment). Due to the fact that the generated potentials are extremely small and buried in noise, repeated stimuli have to be presented to the test subject and the responses have to be averaged to cancel out the random noise and enhance the evoked potentials.

Auditory steady-state response (ASSR) testing also involves monitoring recorded responses from the scalp of tones at varying frequencies. This test is a more sensitive test than the ABR and can also measure residual hearing better.

The Inventor desires an audiometer having at least some of the above- mentioned features and which is usable without a soundproof booth. By way of development, the Inventor further desires an audiometer which can perform a plurality of audiological tests. Preferably, the audiometer is relatively inexpensive.

SUMMARY OF THE INVENTION

Accordingly, the invention provides an audiometer which includes: at least one circum-aural earphone for positioning over an ear of a patient, the circum-aural earphone including: a microphone directed outwardly for receiving external or ambient sound; and an acoustic speaker directed inwardly; at least one inner earphone operatively arranged within the circum-aural earphone, the inner earphone including: an in ear piece for positioning in the ear; a microphone directed outwardly; and an acoustic speaker directed operatively inwardly; and a control module configured to: perform a first phase of active noise reduction using, as an input, sound received by the microphone of the circum-aural earphone and delivering an output via the speaker of the circum-aural earphone; perform a second phase of active noise reduction using, as an input, at least sound received by the microphone of the inner earphone and delivering an output via the speaker of the inner earphone; and emit a hearing-test sound via the speaker of the inner earphone.

Active noise reduction (ANR) is known and the audiometer may make use of existing active noise reduction techniques and algorithms. Active noise reduction is standard technology in many ear protector systems. Patent applications WO0106916, WO0006065 and US6396930 describe methods where ANR is applied to audiometry testing specifically using standard ANR technology. Standard analogue feedback, digital feedback, adaptive feed forward, and adaptive feedback noise control schemes can all be used to actively reduce noise.

The speaker of the inner earphone may be capable of emitting and playing pure-tone air conduction sounds between 125Hz and 2OkHz to the test subject at different volumes (in dB SPL) used to perform tests for hearing levels, DPOAE and ASSR. Furthermore, the speaker may also be operable to emit words and phrases to the test subject at different volumes for speech audiometry testing. Furthermore, the speaker may also be operable to emit click stimuli for ABR.

The circum-aural earphone may include a muff shaped and dimensioned to fit snugly over the ear and abut against a head of the patient, thereby to achieve passive noise reduction. The muff may include a sound-absorbing or sound-insulating material, such as foam or gel. The circum-aural earphone may include at least one sensor on or in the muff and in which the control module may then be configured to determine, by means of the sensor, whether or not the muff abuts properly against the head. The sensor may be in the form of a pressure sensor in order to determine whether or not the muff abuts against a side of the patient's head to perform sufficient passive noise reduction.

Further, the control module may be configured to: determine the difference in volume between the sound received by the microphone of the circum-aural earphone relative to that received by the microphone of the inner earphone; and to provide an indication in response to the difference in volume being below a threshold level, thereby to indicate whether or not the ambient sound is being sufficiently reduced.

In other words, if the difference in volume is below the threshold level, i.e. relatively small, this may mean that the circum-aural earphone is not performing adequate noise reduction (either active or passive). The patient or other operator may then wish to readjust the audiometer or otherwise check why inadequate noise reduction is being achieved.

If desired, the control module may be configured to perform the second phase of active noise reduction using as an input the sound received from both the microphone of the circum-aural earphone and the microphone of the inner earphone. The sounds received from the respective microphones may be weighted as desired, with the weight of the sound received from the microphone of the inner earphone ranging from very small (e.g. 1 %) to maximum (100%) and the weight of the sound received from the microphone of the circum-aural earphone correspondingly ranging from very large (e.g. 99%) to zero (0%). For instance, the sound received from the microphone of the circum-aural earphone may have a weight of 20% while the sound received from the microphone of the inner earphone may have a weight of 80%.

The in ear piece may include at least one sensor and the control module may be configured to determine, by means of the sensor, whether or not the in ear piece is satisfactorily seated within the ear. In other words, if the in ear piece is loose or otherwise fitted in properly, the patient or operator may receive an indication of such.

The in ear piece may include a disposable tip. The in ear piece may be shaped and dimensioned to fit snugly within the ear, thereby to achieve passive noise reduction. For instance, the disposable tip may be of a deformable material, to mould to the shape of the ear. The in ear piece may be in the form of an "earbud" which is designed to be seated in the ear at the entrance to the ear canal, or maybe in the form of a "canalphone" designed to be inserted directly into the ear canal. Furthermore, the in ear piece may include a tip with a circum-tip bladder that can be inflated with fluid.

The audiometer may include a pressure control unit and a pressure sensor in communication with the inner earphone, to vary a pressure delivered to the inner ear of the patient and measure the response, in use, thereby to conduct tympanometry. The audiometer may thus be suitable for conducting a plurality of types of ear tests.

In one embodiment, the inner earphone may include a sound-conducting conduit in communication with the circum-aural earphone and the in ear piece. In such case, the speaker of the inner earphone may be housed within the circum-aural earphone and sound may then be conducted from the speaker along the conduit to the in ear piece. The conduit may be of a flexible material, allowing selective positioning of the in ear piece. The circum-aural earphone may include a receiving formation to receive the in ear piece, the receiving formation having a microphone operable to measure sound emitted from the in ear piece thereby to test the calibration of the inner earphone. The receiving formation may be on an exterior of the circum-aural earphone. The purpose of the receiving formation may be to monitor or calibrate quality of the sound emitted by the in ear piece (before or after noise reduction).

The control module may be configured provide an indication in response to ambient sound detected by the microphone of the circum-aural earphone being above a threshold level. In other words, if there is too much ambient noise which is likely to interfere with the audiometer, the patient or operator may receive an early warning thereof. Another manner in which to ensure that noise is being sufficiently reduced may be to introduce a known sound (either by means of an external speaker or of one of the internal speakers) and compare, by means of the control module, that known sound with sound received by one of the corresponding microphones, thereby quantitatively to measure the degree of noise reduction.

Each of the circum-aural and inner earphones may be one of a pair of such earphones, and the circum-aural earphones may be interconnected and bridged by an arcuate headband. In other words, the audiometer may resemble conventional headphones.

The audiometer may include a bone vibrator arrangement having a bone vibrator to perform bone conduction tests. The bone vibrator arrangement may include a displaceable support arm to allow selective positioning of the bone vibrator against either the forehead or a mastoid. And one embodiment, the displaceable support arm may be pivotally connected to a middle of the headband for positioning the bone vibrator against the forehead. In another embodiment, the displaceable support arm may be pivotally connected to an exterior of the circum-aural earphone for positioning the bone vibrator against a mastoid. One or both of the circum-aural earphones may include a bone vibrator arrangement.

The bone vibrator arrangement may include a compliance pad having a cavity with a microphone to test whether or not the bone vibrator is calibrated. The compliance pad may be positioned on an exterior of the circum-aural earphone. The control module may then be operable to compare a sound received by the microphone of the compliance pad against a predefined sound thereby to determine whether or not the bone vibrator is calibrated within acceptable limits.

The bone vibrator arrangement may include a pressure sensor and the control module may be configured to determine, by means of the pressure sensor, whether or not a pressure with which the bone vibrator is applied to the head is within a predefined range. The bone vibrator arrangement may include an actuator operable to vary the pressure with which the bone vibrator is applied to the head. The control module may then be configured to apply, by means of the actuator, the bone vibrator to the head with a greater pressure when the bone vibrator is active, and with a lesser pressure when the bone vibrator is inactive.

The bone vibrator arrangement may include an electrode and in which the control module is configured to determine, by means of the electrode, whether or not the bone vibrator makes sufficient contact with the skin. It is to be appreciated that in such case the audiometer may include at least one other electrode positionable against another part of the skin of the head, and thereby to determine the resistance between the electrode of the bone vibrator arrangement and the other such electrode.

The audiometer may include electrodes connectable to the head, operable to measure auditory evoked responses.

The audiometer may include at least one sensor operable to sense orientation or motion of the head, in use. The at least one sensor may include at least one of an accelerometer and an inclinometer.

The inner earpiece may include a temperature sensor to measure a temperature of at least a part of the ear.

The audiometer may include an electronic port for connection to a computer.

The invention extends to a method of conducting audiometry, the method including: performing a first phase of active noise reduction by means of a circum-aural earphone; performing a second phase of active noise reduction by means of an inner earphone operatively arranged within the circum-aural earphone; and emitting a hearing-test sound via the inner earphone The method may be practicable in noisy environments without the use of a soundproof booth.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be further described, by way of example, with reference to the accompanying diagrammatic drawings.

In the drawings:

Figure 1 shows a three-dimensional view of an audiometer in accordance with the invention positioned on a head of a patient, in use;

Figure 2 shows a cross sectional schematic view of the audiometer of Figure 1 ; and

Figure 3 shows a side view of the audiometer of Figure 1 .

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring to the drawings, reference numeral 100 indicates an audiometer in accordance with the invention. The audiometer 100 includes a pair of circum-aural earphones 102 (only one of which is illustrated in some of the drawings) for positioning over the ears of a patient. The circum-aural earphone 102 includes a hemi-spherical cup 201 and a muff 215 of foam on an inner side thereof for fitting around and abutting against the ear of the patient, in use. The cup 201 of the circum-aural earphone 102 additionally serves as a housing and mounting for many of the components of the audiometer 100. The cups 201 are bridged and interconnected by a headband and spring members 308.

The circum-aural earphone 102 includes a microphone 202 directed outwardly for receiving external or ambient sound and an acoustic speaker directed inwardly 238. The microphone 202 and the speaker 238 are used for a first phase of active noise reduction (see further below).

The audiometer 100 also includes a pair of inner earphones, generally indicated by reference numeral 104. Each inner earphone 104 is operatively arranged within the associated circum-aural earphone 102. Each inner earphone 104 includes an in ear piece 106 for positioning in the ear, a microphone 230 a directed outwardly and an acoustic speaker 220, 221 directed operatively inwardly. Similarly, the microphone 230 and the speaker 220, 221 are used for a second phase of active noise reduction (see further below).

The audiometer 100 includes housed within the circum-aural earphone 102 a control module (not illustrated). The control module may be a conceptual module corresponding to a task performed the audiometer 100 or an associated computer (not illustrated). To this end, audiometer 100 may include a processor and a machine readable medium (not illustrated) for instance in the form of a memory module, which carries a set of instructions to direct the operation of the processor. It is to be understood that the control module may be one or more microprocessors, controllers, digital signal processors (DSPs), or any other suitable computing device, resource, hardware, software, or embedded logic. It is also to be appreciated that, while control module could be consolidated into the audiometer 100, as in this example, components of the control module could instead be distributed among a number of devices, for example distributed among the audiometer 100 and a networked computer.

The control module is configured to perform two phases of active noise reduction (ANR). This active noise reduction may be performed using conventional ANR methods and algorithms (mentioned above). More particularly, the control module is configured to perform a first phase of active noise reduction using, as an input, sound received by the microphone 202 of the circum-aural earphone 102 and delivering an output via the speaker 238. Additionally, the control module is configured to perform a second phase of active noise reduction using, as an input, at least sound received by the microphone 230 of the inner earphone 104 and delivering an output via the speaker 220, 221 . If desired, for the second phase of noise reduction, the control module could use as an input sound received from the microphone 202 and the microphone 230.

The control module is also configured to emit a hearing-test sound via the speaker 220, 221 of the inner earphone 104 thereby to conduct pure tone air conduction hearing tests.

The circum-aural earphones 102 include sensors 213, 214 positioned on the muff 215 and the control module is configured to determine, by means of the sensors 213, 214, in use whether or not the circum-aural earphone 102 makes sufficient contact with the head.

The control module is additionally configured to determine the difference in volume between the sound received by the microphone 202 of the circum-aural earphone 102 relative to that received by the microphone 230 of the inner earphone 104 and to provide an indication in response to the of the difference in volume being below a threshold level, thereby to indicate whether or not the ambient sound is being sufficiently reduced. Instead, on addition, an additional microphone 203 may be provided inside the 201 , in which case the difference in volume can be determined relative to microphones 202, 203. The indication may be provided by a display arrangement, such as a light emitter, on the audiometer 100, or alternatively, on a computer connected to the audiometer 100.

The inner earpiece 104 includes a flexible sound-conducting conduit 224 to conduct sound from the speakers 220, 221 to the in ear piece 106. The in ear piece 106 includes a disposable, a flexible tip 227, 228, 234. The tip 227, 228, 234 in use is inserted into the ear canal 10 and 25 for stimulating the tympanic membrane 226. The tip 227, 228, 234 fits snugly and air tightly within the ear canal 225. The tip 227, 228, 234 could be of or coated with a conducting material, thereby acting as an electrode for measuring auditory evoked responses. The in ear piece 106 may include a temperature sensor 229 for monitoring temperature of the ear canal 225.

The in ear piece 106, together with the cup 201 and muff 215, are of sound- insulating material and therefore perform passive noise reduction.

The audiometer 100 includes a pressure control unit 216 in fluid communication with the conduit 224 thereby to vary a pressure delivered to the inner ear of the patient thereby to conduct tympanometry. In this regard, the audiometer 100 further includes a pressure sensor 218 and a pressure release valve 219 to equalise pressure within the conduit 224 relative to ambient pressure. A separate conduit 222 interconnects the pressure sensor 218 and valve 219 with the speakers 220, 221 . The cup 201 defines to receiving formations 204, 239. The first receiving formation 239 includes two sockets for receiving and testing sound emission of the respective inner earpieces 104. The second receiving formation 204 includes one socket 205 and a pressure sensor 254 testing whether or not the inner earpiece 104 is airtight.

The control module is configured to provide an indication if ambient sound measured by the microphone 202 is above a certain threshold. In other words, if the environment in which the patient wishes to use the audiometer 100 is so noisy that sufficient noise reduction will not be possible, an indication of this is provided.

The audiometer 100 includes bone vibrator arrangements. A first bone vibrator arrangement includes a bone vibrator 303 connected to the headband of the audiometer 100 via a flexible, displaceable arm 304. Additionally, the bone vibrator arrangement includes a counteracting piece 301 connected via a spring 302 and an electrode 328, a spring housing 307 which supports a bone vibrator calibration unit 306 having a microphone 315 in a cavity 316. The bone vibrator 303 includes pressure sensors 305, 312 for sensing a pressure exerted by the bone vibrator 303 onto the head. An actuator includes a cam member 317 for varying the pressure exerted by the bone vibrator 303. The actuator is under control of the control module which is configured to apply the bone vibrator 303 with a higher pressure during use and relieve the pressure of the bone vibrator 303 when it is inactive, thus avoiding pain or discomfort.

A second bone vibrator arrangement includes a bone vibrator 31 1 swivelably mounted to the cup 201 of each circum-aural earphone 102 by means of a spring arm 233. The second bone vibrator arrangement is swivelable so that the bone vibrator 209 can be aligned with, on the one hand, the mastoid of the patient and, on the other hand, a compliance pad 314 which includes a microphone and which is operable to test whether or not the bone vibrator 209 is operating within predefined parameters.

The second bone vibrator arrangement and compliance pads 314 are shown in more detail in Figure 2. The compliance pad 314 includes a membrane or diaphragm 208 arranged at the mouth of a cavity 207 with a microphone 206 dispersed within the cavity for receiving vibrations imparted by the bone vibrator 209. As mentioned above, the bone vibrator 209 includes a pressure sensor 210, 21 1 for sensing the pressure with which the bone vibrator 209 is applied to the head of the patient. The spring arm 233 is connected to the cup 201 at pivot point 212.

The control module is configured to receive sounds or vibrations measured by the microphones 206, 315 for calibration and measurement. Similarly, the microphone is in electronic communication with the pressure sensors 305, 312, 210,

21 1 in order to determine whether or not the pressure with which the bone vibrators 209, 303 are applied to the head or skull is within an acceptable range.

More particularly, the bone vibrator 209 will play a sound, typically a sweep from 125Hz to 8kHz or a white noise that will be recorded by the microphone 206 of the compliance test pad 314. Verification will then be performed by the control module to test whether these recorded sounds are still within limits (about 3dB on all frequencies) to the original calibrated sounds recorded. If the compliance test is in certain limits, then the operator can trust that the bone vibrator is still calibrated. During this compliance test period, the pressure at which the bone vibrator 209 presses against the compliance pad 314 is also measured to make sure that the force at which the bone vibrator 209 presses against the compliance pad 314 is the same as when the initial calibrated compliance recording was done. If the pressure is not within certain limits to the original compliance test, the patient or operator will then be prompted that the bone vibrator 209 might not be calibrated any more. Also, during the period of testing whether the bone vibrator 209 is still calibrated, the external microphone 202 will record the ambient noise levels to make sure that the ambient noise will not have an effect on the compliance test done. If the volume of the ambient sound is over a certain limit, the test will be aborted and the control module will prompt the operator to change the environment ambient sound levels so as to redo the test. If the compliance test is within limits and the pressure that the bone vibrator presses against the compliance pads is correct and the ambient noise when the compliance test was done was within limits, an operator performing a real time bone vibration test from a remote location can trust the that the bone vibrator 209 is still calibrated and not faulty. Furthermore, the operator can also trust that the bone vibrator 209 was calibrated when the test he is evaluating was done in a store-and-forward telemedicine set-up. The pressure at which the bone vibrator 209 (or 303) presses against the bone is important. If the pressure is too high, then the bone vibrator 209, 303 will produce incorrect tones and if the pressure is too soft, then the contact to the bone through the skin is not good enough meaning that the bone vibration energy will not be transferred to the bone causing incorrect sound transmission to the bone. To ensure the pressure is within limits (roughly 5Nm), a pressure sensor 305, 210, 21 1 between the bone vibrator 209, 303 and the skin will indicate whether the pressure was correct. The spring arm 233, 304 is used to create a constant force on the bone vibrator 209, 303 applied to the forehead or mastoid bones. The user will be prompted whenever this force is incorrect. This verification is good medical practice for audiologists performing a bone vibration pure tone test, and the operator can trust that the bone vibrator 209, 303 was applied correctly and that the spring arm 233, 304 has not worn out even in a telemedical test situation. The operator applying the bone vibrator 209, 303 to the forehead or mastoid could have visual feedback whether regarding whether or not the pressure is within limits by using tycho-trophic materials that changes colour depending on the pressure applied thereto.

Additionally, the microphone 230 of the inner earpiece 104 could be configured to measure bone vibrator sound in each ear and the control module could then be configured to verify, by comparing the sounds measured in each ear, that the bone vibrator sounds are the same amplitude, meaning the bone vibrator 303 was placed centrally on the forehead.

The audiometer includes a magnetic compass 237 and an accelerometer 223 for sensing orientation or motion of the head to which the audiometer 100 is fitted.

The audiometer 100 may include an electronic port, such as a USB or like communication port, for connection to a computer. Various functions of the audiometer 100 may be controlled via the computer and/or statistics from tests may be stored on the computer. In one embodiment, the inner earpiece 104 further includes a thermometer or temperature sensor 231 and a humidity sensor 232 for sensing the temperature of the conduit to 24, which may be used for compensating for temperature changes.

The electrodes (as mentioned above) can be in the form a very thin Ag/AgCI electrode and can be use with electrode gel, or a dry electrode can be used.

The Inventor believes that the fact that so many of the measurement apparatus, such as sensors or microphones, can be tested for compliance within predefined ranges, render the audiometer ideal for use in a telemedicine environment where an operator is not physically present to check the audiometer 100.

By way of development, the Inventor submits that the audiometer 100 could include the following: the bone vibrator 209 could be applied to the head by means of agile or have a larger surface or be of different materials to avoid causing pain; the control module could be configured to determine from which side noise interference originates and indicate that the test be performed on the other side; the control module could be configured to determine the frequency of the noise and whether or not noise of that frequency would interfere with a particular taste; the control module could be configured to monitor any sound distortion caused by noise cancellation; a microphone to measure noise originating from inside the ear to detect objective tinnitus; a heart beat measurer; a camera directed towards the eardrum; loose, hanging electrodes; patient communication - talk to patient thought air or bone; a microphone to measure noise generated for components inside e.g. pressure control unit the ability to do double sided tympanometry simultaneously and test contra and ipsi-lateral reflexes at same time while presenting loud tone only in one ear; the ability to blow air on eardrum - cold/hot to test for nystagmus; a backup: if one side breaks can turn around; a face illustrated on the cup 201 to indicate front and back; and a connector for a response button.

Additionally, the audiometer 100 could be combined with: a scale to measure height; a nystagmus meter to measure positional nystagmus; a camera to view tympanic membrane; a spectacles to do visual evoked responses; an EEG; an ICG; an ECG to test the difference between QRS to pulse time left and right indication of carotid atherosclerosis; built-in pulse oximetry; a tinnitus microphone; an internal microphone inside cup housing pick up heartbeat; a microphone to pick up scratching on cup of for instance clothes; an arrangement for remote testing in a telemedicine environment; a plethysmograph form difference between different levels; and a small bladder that pump up to seal ear canal.

It is an advantage of the invention as exemplified that the audiometer 100 is a multiple-use audiometer capable of performing multiple audiometry tests, including pure-tone air conduction audiometry, pure-tone bone conduction audiometry, tympanometry, speech audiometry testing (specifically speech discrimination threshold testing and speech reception threshold testing (SRT)) as well as auditory brain stem response testing. Other tests that can be combined with this audiometer 100 include imaging of the ear canal and tympanic membrane, as well as oxymetry and an infra-red temperature monitoring.

Conventional audiometry requires very low ambient noise levels in order to determine a hearing threshold level of the patient. The Inventor submits that no sound booth is needed for the audiometer in accordance with the invention to perform the aforementioned testing. The Inventor submits that the combination passive noise reduction by means of the circum-aural earphone 102 and the in ear piece 106 together with the two phases of active noise reduction provides a very large noise reduction ratio (NRR) compared to existing audiometry devices and that NRR values of up to 60dB's can be reached. More particularly, and without wishing to be bound by theory, the Inventor speculates that noise reduction achieved by the circum-aural earphone 102 will be in the region of 33dB's. The reduction per frequency is typically as follows: 125Hz - 25dB, 250Hz - 29dB, 500Hz - 37dB, 1 kHz - 4OdB, 2kHz - 35dB, 4kHz - 39dB, 6kHz - 41dB, 8kHz - 41 dB. With a good seal between the in ear piece 106 and the ear, the further NRR is between 23dB to 30dB's. The reduction per frequency is typically as follow: 125Hz - 33dB, 250Hz - 35dB, 500Hz - 35dB, 1 kHz - 35dB, 2kHz - 33dB, 4kHz - 4OdB, 8kHz - 44dB. No existing audiometry device of which the Inventor is aware can achieve comparable noise reduction figures. The double ANR might increase this NRR even more.

Claims

CLAIMS:

1 . An audiometer which includes: at least one circum-aural earphone for positioning over an ear of a patient, the circum-aural earphone including: a microphone directed outwardly for receiving external or ambient sound; and an acoustic speaker directed inwardly; at least one inner earphone operatively arranged within the circum-aural earphone, the inner earphone including: an in ear piece for positioning in the ear; a microphone directed outwardly; and an acoustic speaker directed operatively inwardly; and a control module configured to: perform a first phase of active noise reduction using, as an input, sound received by the microphone of the circum-aural earphone and delivering an output via the speaker of the circum-aural earphone; perform a second phase of active noise reduction using, as an input, at least sound received by the microphone of the inner earphone and delivering an output via the speaker of the inner earphone; and emit a hearing-test sound via the speaker of the inner earphone.

2. An audiometer as claimed in claim 1 , in which the circum-aural earphone includes a muff shaped and dimensioned to fit snugly over the ear and abut against a head of the patient, thereby to achieve passive noise reduction.

3. An audiometer as claimed in claim 2, in which the circum-aural earphone includes at least one sensor on or in the muff and in which the control module is configured to determine, by means of the sensor, whether or not the muff abuts properly against the head.

4. An audiometer as claimed in any of the preceding claims, in which the control module is configured to: determine the difference in volume between the sound received by the microphone of the circum-aural earphone relative to that received by the microphone of the inner earphone; and to provide an indication in response to the difference in volume being below a threshold level, thereby to indicate whether or not the ambient sound is being sufficiently reduced.

5. An audiometer as claimed in any of the preceding claims, in which the control module is configured to perform the second phase of active noise reduction using as an input the sound received from both the microphone of the circum-aural earphone and the microphone of the inner earphone.

6. An audiometer as claimed in any of the preceding claims, in which the in ear piece includes at least one sensor and in which the control module is configured to determine, by means of the sensor, whether or not the in ear piece is satisfactorily seated within the ear.

7. An audiometer as claimed in any of the preceding claims, in which the in ear piece includes a disposable tip.

8. An audiometer as claimed in any of the preceding claims, in which the in ear piece is shaped and dimensioned to fit snugly within the ear, thereby to achieve passive noise reduction.

9. An audiometer as claimed in any of the preceding claims, which includes a pressure control unit and a pressure sensor in communication with the inner earphone, to vary a pressure delivered to the inner ear of the patient and measure the response, in use, thereby to conduct tympanometry.

10. An audiometer as claimed in any of the preceding claims, in which the inner earphone includes a sound-conducting conduit in communication with the circum- aural earphone and the in ear piece.

1 1 . An audiometer as claimed in claim 10, in which the speaker of the inner earphone is housed within the circum-aural earphone and in which sound is conducted from the speaker along the conduit to the in ear piece.

12. An audiometer as claimed in claim 1 1 , in which the circum-aural earphone includes a receiving formation to receive the in ear piece, the receiving formation having a microphone operable to measure sound emitted from the in ear piece thereby to test the calibration of the inner earphone.

13. An audiometer as claimed in any of the preceding claims, in which the control module is configured provide an indication in response to ambient sound detected by the microphone of the circum-aural earphone being above a threshold level.

14. An audiometer as claimed in any of the preceding claims, in which each of the circum-aural and inner earphones is one of a pair of such earphones, and in which the circum-aural earphones are interconnected and bridged by an arcuate headband.

15. An audiometer as claimed in claim 14, which includes a bone vibrator arrangement having a bone vibrator to perform bone conduction tests.

16. An audiometer as claimed in claim 15, in which the bone vibrator arrangement includes a displaceable support arm to allow selective positioning of the bone vibrator against either the forehead or a mastoid.

17. An audiometer as claimed in claim 15 or claim 16, in which the bone vibrator arrangement includes a compliance pad having a microphone to test whether or not the bone vibrator is calibrated.

18. In audiometer as claimed in claim 17, in which the control module is operable to compare a sound received by the microphone of the compliance pad against a predefined sound thereby to determine whether or not the bone vibrator is calibrated within acceptable limits.

19. An audiometer as claimed in any of claims 15 to 18 inclusive, in which the bone vibrator arrangement includes a pressure sensor and in which the control module is configured to determine, by means of the pressure sensor, whether or not a pressure with which the bone vibrator is applied to the head is within a predefined range.

20. An audiometer as claimed in any of claims 15 to 19 inclusive, in which the bone vibrator arrangement includes an actuator operable to vary the pressure with which the bone vibrator is applied to the head.

21 . An audiometer as claimed in claim 20, in which the control module is configured to apply, by means of the actuator, the bone vibrator to the head with a greater pressure when the bone vibrator is active, and with a lesser pressure when the bone vibrator is inactive.

22. An audiometer as claimed in any of claims 15 to 21 inclusive, in which the bone vibrator arrangement includes an electrode and in which the control module is configured to determine, by means of the electrode, whether or not the bone vibrator makes sufficient contact with the skin.

23. An audiometer as claimed in any of the preceding claims, which includes electrodes connectable to the head, operable to measure auditory evoked responses.

24. An audiometer as claimed in any of the preceding claims, which includes at least one sensor operable to sense orientation or motion of the head, in use.

25. An audiometer as claimed in claim 24, in which the at least one sensor includes at least one of an accelerometer and an inclinometer.

26. An audiometer as claimed in any of the preceding claims, in which the inner earpiece includes a temperature sensor to measure a temperature of at least a part of the ear.

27. An audiometer as claimed in any of the preceding claims, which includes an electronic port for connection to a computer.

28. A method of conducting audiometry, the method including: performing a first phase of active noise reduction by means of a circum-aural earphone; performing a second phase of active noise reduction by means of an inner earphone operatively arranged within the circum-aural earphone; and emitting a hearing-test sound via the inner earphone.