GB2573763A

GB2573763A - Method for setting up an unreferenced audio system to perform a supra-threshold hearing test

Info

Publication number: GB2573763A
Application number: GB1807838.6A
Authority: GB
Inventors: Schönfelder Vinzenz; Clark Nick
Original assignee: Mimi Hearing Technologies GmbH
Current assignee: Mimi Hearing Technologies GmbH
Priority date: 2018-05-15
Filing date: 2018-05-15
Publication date: 2019-11-20
Also published as: GB201807838D0

Abstract

An unreferenced audio system is set up in order to perform a supra-threshold hearing test by presenting a stimulus component to a human ear of a user on the uncalibrated audio system, providing instructions to the user, and receiving an input from the user to adjust the digital level of the stimulus presented through the audio system. Thus the subject’s baseline audible stimulus threshold is determined in relation to the device, and the device’s volume level is adjusted to calibrate the device before carrying out the hearing test. The audio device may be a consumer device with a touch screen interface for receiving user input. An app on the consumer device may be used instruct the user in setting up the device. The instruction may be to change the volume of the device.

Description

METHOD FOR SETTING UP AN UNREFERENCED AUDIO SYSTEM TO PERFORM A SUPRA-THRESHOLD HEARING TEST

FIELD OF THE INVENTION

The present invention relates to a method of setting up an unreferenced or noncalibrated audio system to perform a supra-threshold hearing test.

BACKGROUND

Human perception of stimuli through the respective senses, i.e. sight, hearing, touch, balance, taste and smell, depends on properties of the stimuli and an individual’s ability to identify and discriminate different stimuli. In the case of sound, the healthy human ear is capable of detecting sounds within the frequency range of 20 Hz to 20,000 Hz, i.e. the human ear has a lower frequency threshold of 20 Hz and an upper frequency threshold of 20,000 Hz. As the individual ages, the upper frequency threshold tends to reduce.

Perception of sound intensity also varies from individual to individual. Exposure to high intensity sound can cause damage to human hearing including partial or total hearing loss at certain frequencies. In a condition known as hyperacusis, a patient suffers from increased sensitivity to certain frequencies and sound amplitudes - often to a debilitating degree.

It is recognized that the lowest sound intensity detectable by an individual is dependent on the frequency of the sound. In general, the lower limit of audible sound intensity is 0 dB hearing level (HL) for a young healthy individual, where dB HL is a frequency adjusted measure that accounts for the differences in human sensitivity to sound intensity across frequency. A threshold of greater than 25 dB HL for any frequency in the audiometric range (0.25 - 8 kHz) is considered to correspond to a clinically diagnosable hearing loss.

An individual’s auditory threshold can be determined by way of a pure tone threshold test. A pure tone threshold test involves delivering a pure tone sound to the ear with no other sound present. Such a test is typically performed under clinical or laboratory conditions in a soundproof box or room. An example of a pure tone threshold test requires an individual to press a button each time they hear a sound to record the instances where a sound of a certain frequency and level has been detected by the individual. A clinician can then identify the lowest sound intensity that the individual’s ear is capable of detecting. Another test example requires a continuous tone to be delivered to the individual’s ear.

There are different kinds of hearing tests that provide more and richer information about the state of a user’s hearing, and of the function of different components within the ear. For example, psychophysical tuning curve (PTC) tests represent a class of supra-threshold tests that estimate the spectral resolution of the auditory system. Data from supra-threshold tests can be used to more effectively set up a hearing instrument or personalized audio experience than Minimal Audible Threshold (MAT) alone. By definition, these tests are performed above the MAT and are thus called supra-threshold tests. In laboratory conditions, the stimuli for these test types are often specified at a level in relation to the user's known MAT. MATs are typically measured in terms of the absolute physical sound level, in dB sound pressure level (dB SPL) or dB hearing level (dB HL). As pure tone thresholds are difficult to determine outside clinical or laboratory conditions, this information is often not readily available to the general public. In addition, unreferenced or uncalibrated consumer audio systems, such as smartphones or computers, usually do not allow to precisely deliver audio signals at a specific physical sound level.

However, to perform a supra-threshold test on a consumer digital audio device, it is generally not necessary to know the MAT at an absolute scale. Instead, it is sufficient to determine the threshold level at the internal digital level scale of the device, usually defined in terms of decibels relative to full scale (dB FS). Due to the design of digital audio systems, there are natural limits to the dynamic range of a digital audio system: All sounds are represented as levels at or below 0 dB FS. The lower end of the digital scale is determined by the bit depth of the signal processing, e.g., -96 dB FS for a 16-bit audio system. The device volume setting determines the relationship between the internal digital scale (dB FS) and the physical sound level (dB SPL or HL) generated by the transducers (e.g., headphones or speakers). For example, if the device's volume is set to a higher level, a tone at the particular digital level (defined in dB FS) will result in a louder tone at the transducer compared to a tone at the same digital level played back at a lower device volume. The device volume setting can for example be defined as a ratio of the maximum device output level, e.g. a percentage of the maximum output level. It can be adjusted on the device, for example by the means of one or more volume switches.

In order to successfully perform a supra-threshold test, the digital device must be able to generate sounds at levels above a user's threshold. If the device volume is set too low, the maximum digital signal level (0 dB FS) may not be sufficient to generate loud enough sounds for a successful supra-threshold test. For example, a masking test such as a PTC, may require a headroom of, for example, 50 dB above a user's threshold. If the user's MAT has been determined to be at -10 dB FS on the internal digital scale, the loudest tones during a suprathreshold test could only be presented 10 dB above, which would not be sufficient to adequately perform the test.

On the other hand, if the device volume is set too high, the minimum digital signal (e.g. 96 dB FS) may still be too loud to reliably estimate a user's threshold. In addition, the loudest sounds that a user may hear during a test, may be painful or even harmful to the user. For example, a user's MAT could theoretically be at -100 dB FS in terms of the internal digital scale, but the quietest tones that can be played could be at -96 dB FS. In this case, his or her threshold could not be reliably estimated. In addition, the loudest tones that he or she may hear during the test may be 100 dB above their threshold which will be painful even for normal hearing subjects, let alone hearing-impaired persons.

In conclusion, two challenges need to be solved before a user can perform a suprathreshold test on a consumer device. First, the threshold of the user has to be determined on the device's internal digital scale. Second, the devices external volume setting has to be adjusted in a way so that the conditions for a successful supra-threshold test are fulfilled.

SUMMARY OF THE INVENTION

The present invention seeks to address the aforementioned problems.

An aspect of the present invention provides a convenient method of ensuring the reliability of a supra-threshold hearing test by estimating an audible stimulus threshold. The method comprises the steps of playing a stimulus component at a certain level to a user, receiving an input from the user to adjust the digital level of the stimulus, receiving a confirmation input from the user, evaluating the input from the user to produce an evaluation, and providing information to the user based on the evaluation.

The term ‘stimulus’ as used in this application shall be interpreted as all components of a test sound. The term “stimulus component” shall be interpreted as any signal or masker of a sound being played. The term ‘signal’ shall be interpreted as a positive component of the stimulus that an individual is seeking to identify. ‘Masker’ shall be interpreted as a noise component, or any other competing sound, under test that has the purpose of identifying how effective that sound is at masking a signal. In a supra-threshold test, such as a PTC test, the signal may be a pure tone and the masker may be a narrow band of noise.

Establishment of the absolute auditory thresholds (in dB HL or dB SPL) outside of clinical and laboratory conditions is challenging and typically beyond the capability of an individual using standard consumer devices such as mobile phones, tablets, computers, or audio players, for example. In order to conduct a supra-threshold test of acceptable accuracy, a baseline audible stimulus threshold is required. Such a baseline is provided for in a method according to this aspect of the invention by playing a stimulus component at a certain level to a user, receiving an input from the user to adjust the digital level of the stimulus component, receiving a confirmation input from the user, evaluating the input from the user to produce an evaluation, and providing information to the user based on the evaluation. This information allows the device to estimate a pure tone threshold in terms of the device's internal digital scale (dB FS), which will be used as a base line for the subsequent supra-threshold test, for example, when measuring psychophysical tuning curves (PTC).

When employing the method for estimating PTCs according to S$k & Moore (2011) (Implementation of a fast method for measuring psychophysical tuning curves International Journal of Audiology, 50(4), 237-242), the signal tone is presented at a fixed level relative to the MAT of the user. Therefore, the user would adjust the level of the stimulus component, being a pure tone in this instance, prior to the test in order to find the MAT in terms of dB FS (for example -80 dB FS) and then an amount could be added to ensure that the signal is clearly audible (i.e. the signal could be presented at -60 dB FS, that is 20 dB above the MAT), while near threshold for the remainder of the test.

In one embodiment, the method further comprises setting the device volume setting to a pre-determined level before use of the interface to adjust the digital audio level (dB FS) of the stimulus component.

Setting the device volume setting of the device to a pre-determined level prior to adjusting the digital audio level (dB FS) of the stimulus component facilitates the effective performance of a pure tone threshold test by ensuring the characteristics of the stimulus component are such that it is audible to an individual.

In another configuration, the user may be instructed to set the device volume setting of the device to a pre-defined percentage of the maximal output level at the outset. For example, the user may be instructed to set the device volume to 75%, 80%, or 85% of the maximal output level of the device at the outset. Depending on the device characteristics, this provides a safety net that prevents unpleasantly high intensity signals from being presented to the user during the test, or even signals that exceed the pain threshold of the user. In this instance, a, MAT measurement can be performed and if it is determined that there is not enough headroom for the test type to be conducted, then the user can be instructed to increase the device volume level. A further MAT measurement can then be taken.

In another embodiment of the present invention, the interface comprises a touch screen operable interface.

Use of a touch screen interface to adjust the digital level of the stimulus component is advantageous as nearly all modern consumer devices comprise a touch screen. A further advantage of touch screens is that they allow the presentation of a variety of input interfaces. The display and input spaces can be integrated to save space.

In another preferred embodiment of the present invention, the touch screen operable interface may comprise a slider.

Use of a slider to adjust the stimulus component is advantageous as it is intuitive to an individual using the application that operation of the slider adjusts the output level of the stimulus component upwards or downwards depending on the direction of movement of the slider.

In an embodiment of the present invention, the instruction given by the unreferenced audio system is an instruction to modify the external volume.

During the test, the signal component must be loud enough for the human ear to reliably detect it. Otherwise, the user cannot meaningfully perform the task, and the test results will be erroneous. In another embodiment of the present invention, the user may be asked to increase the volume, for example by 20% of the device volume at the outset, preferably 30% of the device volume at the outset. In a preferred embodiment of the present invention, the user may be prevented from taking the test if the volume of the device is too low. In another preferred embodiment of the present invention, the user may receive a warning that the volume of the device is too low but may still be allowed to take the test.

On the other hand, if the device volume is set too high, the lowest level that the signal component can be presented to the ear may be too high to successfully perform the suprathreshold test. In another embodiment of the present invention, the user may be then asked to reduce the volume, for example by 20% of the device volume at the outset, preferably 30% of the device volume at the outset. In a preferred embodiment of the present invention, the user may be prevented from taking the test if the volume of the device is too high. In another preferred embodiment of the present invention, the user may receive a warning that the volume of the device is too high but may still be allowed to take the test.

The frequency of the stimulus component may be set such that the stimulus component is detectable at a sufficient level by the majority of the population who do not suffer from impaired hearing. Preferably, the frequency of the stimulus component may be between 20 Hz and 20 kHz, preferably between 125 Hz and 16 kHz, more preferably between 250 Hz and 8 kHz, even more preferably between 500 Hz and 4 kHz.

A PTC test may typically be performed for stimulus components between frequencies of 20 Hz and 20 kHz, preferably between 125 Hz and 16 kHz, more preferably between 250 Hz and 8 kHz, even more preferably between 500 Hz and 4 kHz. The frequency of the stimulus component therefore has the advantage of corresponding to typical frequencies of the stimulus component in a PTC test.

In an embodiment of the present invention, the stimulus component is presented at any digital level at or below 0 dB FS. In a preferred embodiment of the present invention, the stimulus component is presented at any level below 0 dB FS, preferable in a range of between 120 dB FS and 0 dB FS.

Defining a limited sound intensity range has the advantage of preventing the pain threshold of the user from being exceeded while also being able to present sufficiently loud stimuli during the test.

In one embodiment, the method further comprises the step of determining whether a supra-threshold test can be performed by comparing the estimated stimulus component threshold with supra-threshold test requirements.

In another embodiment, the method further comprises estimating the remaining dynamic range window of the user. A user first sets the device volume to as loud a level as they still feel comfortable with while playing a continuous near maximum digital signal (0 dB FS or slightly below). Subsequently, with that same device volume, the user adjusts a stimulus component to be close to their hearing threshold. From this procedure, the width of the user’s remaining audible or comfortable auditory range is ascertained. The width of this dynamic range proves valuable in determining whether a supra-threshold hearing test can be successfully performed.

Another aspect of the invention provides a method for estimating MAT of stimuli to be used in hearing tests involving more complex stimuli than a pure tone, the method comprising: performing stimulus component threshold estimation and using the stimulus component threshold estimation as a baseline for a test. Supra-threshold testing includes established tests such as those estimating temporal or spectral resolution of the auditory system, e.g. psychophysical tuning curve (PTC) tests, temporal fine structure (TFS) tests, temporal masking curve measurements, masking level differences, or gap-detection tests, as well as tests estimating equal loudness curves, loudness scaling, or speech comprehension.

Use of a pure tone threshold estimation or stimulus component threshold estimation as a baseline for a supra-threshold test facilitates the carrying out of such a test by an individual using a consumer device. Supra-threshold testing using a consumer device is thus possible using an estimate of MAT in terms of the device's internal digital scale and does not require clinical or laboratory data. In fact, it has been found that there is a high error tolerance regarding minimum audible threshold with regard to obtaining reliable supra-threshold results for many types of tests.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended figures describe the manner in which the above-recited and other advantages and features of the disclosure can be obtained.

Figure 1 shows a situation in which the device volume setting allows a supra-threshold test to be performed. The maximum digital signal level (0 dB FS), i.e. the loudest tones that can be presented to the user, correspond to the user’s individual maximum comfort level. They even may exceed this level slightly. This leaves enough headroom (e.g. a headroom of about 60 dB) for the supra-threshold test to be performed, without risk of harming or causing pain to the user. The relation between internal digital level and external physical level is controlled by the device volume setting as indicated by the double arrow.

Figure 2 illustrates a situation in which the device volume is set too low: the maximum digital signal level (0 dB FS) may be insufficient to generate physically loud enough sounds for a supra-threshold test to be successfully performed because there is too little stimulus headroom above the user’s threshold.

Figure 3 illustrates a situation in which the device volume is set too high: the minimum digital signal level (e.g. -96 dB FS) may still be too loud to reliably estimate a user's threshold. In addition, the loudest sounds that a user may hear during a test, may be painful or even harmful to the user.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Prior to performing a supra-threshold test it is usually necessary to determine an individual’s pure-tone threshold. A pure tone threshold is typically obtained in clinical or laboratory conditions and is very difficult to estimate by a consumer using arbitrary equipment. An even more accurate indicator of the user’s hearing would be to estimate the user’s remaining dynamic range window.

An estimate of pure tone threshold can be determined by presenting a stimulus component to the human ear and requiring the individual to respond ‘yes’ or ‘no’ as to whether they can perceive the stimulus component at different digital audio levels (dB FS). The stimulus component is delivered by a consumer device, for example through the speakers or through a pair of headphones connected to the device. The device volume setting of the consumer device is set to an arbitrary or pre-determined level which may be the maximum or some other predetermined percentage of the maximum volume to present a clear and detectable stimulus component. At the start of the test, the user should be able to clearly detect the stimulus component. If the pre-determined device volume setting does not result in a clearly detectable stimulus component, the individual is prompted to increase the device volume setting, e.g to the maximum level if required.

The stimulus component is initially presented at a frequency between 20 Hz to 20 kHz and at an intensity sufficient to be clearly audible to any individual with hearing within a normal range. An application running on the consumer device is used to adjust the digital audio level (dB FS) of the stimulus component until the user can barely perceive the stimulus component. The level of this barely perceivable stimulus component is used by the application as a baseline for supra-threshold testing.

Different forms of supra-threshold testing may utilize different stimulus component threshold estimations. The present invention is applicable to all supra-threshold tests that utilize a pre-measured or estimated stimulus threshold of an individual.

Some supra-threshold tests, such as a Temporal Fine Structure (TFS) test or a gap detection test, do not rely on masking paradigms. Nevertheless, to effectively perform such a test, the level of the signal needs to be controlled. When using uncalibrated consumer devices, the output level of the stimulus component can vary from device to device. Accordingly, an individual could adjust the output level of the stimulus such that it is tolerable/comfortable to the individual prior to undertaking the test. For example, TFS tests may use a band-limited harmonic complex tone as a stimulus component whose level may be adjusted by the individual prior to the test.

The application running on the consumer device provides an interface to adjust the digital level of the stimulus component according to the individual’s personal hearing characteristics. In the embodiment illustrated in figure 1, the interface is provided by a slider that is operable by use of a touch screen to adjust the stimulus component level. It will be appreciated that the interface design could take any number of forms, i.e. a dial operable by use of a touch screen, a knob operable by use of a touch screen, volume controls on a mobile consumer device, a remote control for a consumer device and gesture control.

In use, an individual accesses a software application on a consumer device. The application automatically adjusts the device volume setting or instructs the user to set the device volume setting to a pre-determined level, for example using the volume buttons of the device. Once the correct device volume setting is set, the application requests the individual to indicate when he/she is ready to start the stimulus component threshold estimation. A stimulus component is output by the device, preferably through a pair of headphones or speakers connected to the device. The application prompts the individual to use an interface, which could be a slider, to adjust the digital audio level (dB FS) of the stimulus component until the stimulus component is perceptible by the individual to a certain extent (for example “barely”, “comfortably”, “almost uncomfortably”). The perceptible stimulus component is then stored by the application for re-use in subsequent supra-threshold testing.

Furthermore, to enable the individual to clearly identify the stimulus component in the test environment a pre-determined level increase may be added to the adjusted digital audio level for the duration of the test. The application will inform the individual if supra-threshold testing cannot be performed based on the individual’s estimated pure tone threshold. A high pure tone threshold estimation could result from impaired hearing, weak sound output, or excessive background noise, for example.

It will be appreciated that foregoing describes embodiments by way of example only and is not intended to limit the scope of the invention which should be interpreted in accordance with the claims.

Claims

1. A method for setting up an unreferenced audio system in order to perform a suprathreshold test, comprising the steps of:

presenting a stimulus component to a human ear of a user on the unreferenced audio system after, or while, instructing the user about a specific task;

receiving an input from the user to adjust the digital level of the stimulus presented through the unreferenced audio system;

receiving a confirmation input from the user;

evaluating the input from the user to produce an evaluation; and providing information to the user based on the evaluation.

2. A method for setting up an unreferenced audio system according to claim 1, further comprising the step of setting the audio device audio level to a pre-determined level before presenting a stimulus component to a human ear of a user on the unreferenced audio system.

3. A method for setting up an unreferenced audio system according to claim 1 or claim 2, wherein the unreferenced audio system comprises an interface.

4. A method for setting up an unreferenced audio system according to claim 3, wherein the interface comprises a touch screen operable interface.

5. A method for setting up an unreferenced audio system according to claim 4, wherein the interface comprises a slider operable by the touch screen operable interface.

6. A method for setting up an unreferenced audio system according to any one of the preceding claims, wherein the information comprises an instruction to modify the external volume.

7. A method for setting up an unreferenced audio system according to any one of the preceding claims, wherein the stimulus component comprises a pure tone signal presented in the frequency range of 20 Hz to 20 kHz and the intensity range of-10 dB to 120 dB HL.

8. A method for setting up an unreferenced audio system according to any one of the preceding claims, wherein the method further comprises the steps of estimating a pure tone threshold from the evaluation and determining whether a supra-threshold test can be performed by comparing the estimated pure tone threshold with supra-threshold test requirements.

9. A method for setting up an unreferenced audio system according to any one of the preceding claims, wherein the method further comprises the step of estimating the remaining dynamic range window of the user.

10. A method for setting up an unreferenced audio system according to any of the preceding claims, wherein the method further comprises the steps of estimating a pure tone threshold from the evaluation and using the estimated pure tone signal threshold as a baseline for suprathreshold testing.