Presbycusis or Age Related Hearing Loss (ARHL) is the most common type of hearing loss in the elderly. ARHL is characterized by (1) a loss of hearing sensitivity and (2) a decreased ability to understand speech in the presence of background noise (the “cocktail party effect”). Conventional amplification techniques can be very helpful for overcoming the loss of sensitivity. But conventional techniques have provided a much lower degree of success at overcoming the inability to understand speech.
One aspect of the invention is directed to a first hearing assist apparatus. The first hearing assist apparatus comprises a microphone that generates a first signal; and a set of at least four band-stop filters arranged in series. Each of the band-stop filters has a respective center frequency and a respective bandwidth, and the first signal is filtered by each of the at least four band-stop filters in series to yield a second signal. The first hearing assist apparatus also comprises an audio frequency amplifier configured to drive a speaker with an amplified version of the second signal.
In some embodiments of the first hearing assist apparatus, the center frequencies of all the band-stop filters are positioned at regular intervals on a linear scale. In some embodiments of the first hearing assist apparatus, the spacing in frequency between the center frequency of any given band-stop filter and the center frequency of a subsequent band-stop filter is at least two times the bandwidth of the given band-stop filter. In some embodiments of the first hearing assist apparatus, each of the band-stop filters has an order N of at least 6 and a stop band gain that is below −9 dB. In some embodiments of the first hearing assist apparatus, the set of filters has between 8 and 20 band-stop filters arranged in series. Some embodiments of the first hearing assist apparatus further comprise the speaker.
In some embodiments of the first hearing assist apparatus, the center frequencies of all the band-stop filters are positioned at regular intervals on a linear scale, and the size of the regular intervals is user-adjustable. Optionally, in these embodiments, each of the band-stop filters has the same bandwidth B, and B is user-adjustable. Optionally, in these embodiments, the set of filters has between 8 and 20 band-stop filters arranged in series.
Another aspect of the invention is directed to a second hearing assist apparatus. The second hearing assist apparatus comprises a microphone that generates a first signal; and a digital filter having at least four audio frequency stop bands, with an audio frequency pass band positioned between adjacent stop bands. Each of the stop bands has a respective center frequency and a respective bandwidth, and the digital filter inputs the first signal and generates a corresponding filtered second signal as an output. The second hearing assist apparatus also comprises an audio frequency amplifier configured to drive a speaker with an amplified version of the second signal.
In some embodiments of the second hearing assist apparatus, the center frequencies of all the stop bands are positioned at regular intervals on a linear scale. In some embodiments of the second hearing assist apparatus, the spacing in frequency between the center frequency of any given stop band and the center frequency of a subsequent stop band is at least two times the bandwidth of the given stop band. In some embodiments of the second hearing assist apparatus, each of the stop bands has an order N of at least 6 and a stop band gain that is below −9 dB. In some embodiments of the second hearing assist apparatus, the digital filter has between 8 and 20 stop bands. Some embodiments of the second hearing assist apparatus further comprise the speaker.
In some embodiments of the second hearing assist apparatus, the center frequencies of all the stop bands are positioned at regular intervals on a linear scale, and the size of the regular intervals is user-adjustable. Optionally, in these embodiments, each of the stop bands has the same bandwidth B, and B is user-adjustable. Optionally, in these embodiments, the digital filter has between 8 and 20 stop bands.
Another aspect of the invention is directed to a first method of processing an audio signal to assist a person's hearing. The first method comprises inputting the audio signal; and filtering the audio signal using a filter that has between 8 and 20 audio frequency stop bands, with an audio frequency pass band positioned between adjacent stop bands. Each of the stop bands has a respective center frequency and a respective bandwidth, and each of the stop bands has an order N of at least 6 and a stop band gain that is below −9 dB. The first method also comprises generating an output signal based on the filtered audio signal.
In some instances of the first method, the center frequencies of all the stop bands are positioned at regular intervals on a linear scale. In some instances of the first method, the spacing in frequency between the center frequency of any given stop band and the center frequency of a subsequent stop band is at least two times the bandwidth of the given stop band. In some instances of the first method, the center frequencies of all the stop bands are positioned at regular intervals on a linear scale, and the size of the regular intervals is user-adjustable.
Another aspect of the invention is directed to a third telecommunication apparatus. The third telecommunication apparatus comprises a first processor configured to convert a microphone output signal to outgoing data; and a transceiver configured to transmit the outgoing data and to receive incoming data. The third telecommunication apparatus also comprises a second processor configured to (a) extract a first signal from the incoming data and (b) process the first signal using a digital filter and generate a corresponding filtered second signal as an output. The digital filter has at least four audio frequency stop bands, with an audio frequency pass band positioned between adjacent stop bands. Each of the stop bands has a respective center frequency and a respective bandwidth. The third telecommunication apparatus also comprises an audio frequency amplifier configured to drive a speaker with an amplified version of the second signal. The third telecommunication apparatus also comprises a controller programmed to output an audio signal that corresponds to a set of words to the digital filter for processing, and accept a user adjustment of parameters of the digital filter that provides the user with improved intelligibility.
In some embodiments of the third telecommunication apparatus, the controller, the first processor, and the second processor are all implemented in a single integrated circuit. In some embodiments of the third telecommunication apparatus, added noise is included in the audio signal that corresponds to the set of words. In some embodiments of the third telecommunication apparatus, the center frequencies of all the stop bands are positioned at regular intervals on a linear scale.
Another aspect of the invention is directed to a second method of processing an audio signal to assist a person's hearing. The second method comprises generating a first audio signal that corresponds to a given set of words; and filtering the first audio signal using a digital filter that has between 8 and 20 audio frequency stop bands, with an audio frequency pass band positioned between adjacent stop bands. Each of the stop bands has a respective center frequency and a respective bandwidth. The second method also comprises outputting the filtered version of the first audio signal to a user; accepting, from the user, at least one adjustment to a set of parameters for the digital filter; and storing a set of user-preferred parameters for the digital filter based on the accepting step. The second method also comprises inputting a second audio signal; filtering the second audio signal using the digital filter, using the stored set of user-preferred parameters; and generating an output signal based on the filtered second audio signal.
In some instances of the second method, added noise is included in the first audio signal. In some instances of the second method, the center frequencies of all the stop bands are positioned at regular intervals on a linear scale. In some instances of the second method, a spacing in frequency between the center frequency of any given stop band and the center frequency of a subsequent stop band is at least two times the bandwidth of the given stop band. In some instances of the second method, the center frequencies of all the stop bands are positioned at regular intervals on a linear scale, and a size of the regular intervals is user-adjustable. In some instances of the second method, each of the stop bands has an order N of at least 6 and a stop band gain that is below −9 dB.
Another aspect of the invention is directed to a fourth telecommunication apparatus. The fourth telecommunication apparatus comprises a first processor configured to convert a microphone output signal to outgoing data; and a transceiver configured to transmit the outgoing data and to receive incoming data. The fourth telecommunication apparatus also comprises a second processor configured to (a) extract a first signal from the incoming data and (b) process the first signal using a digital filter and generate a corresponding filtered second signal as an output. The digital filter has at least four audio frequency stop bands, with an audio frequency pass band positioned between adjacent stop bands. Each of the stop bands has a respective center frequency and a respective bandwidth, and the center frequencies of all the stop bands are positioned at regular intervals on a linear scale. And the fourth telecommunication apparatus also comprises an audio frequency amplifier configured to drive a speaker with an amplified version of the second signal.
In some embodiments of the fourth telecommunication apparatus, a spacing in frequency between the center frequency of any given stop band and the center frequency of a subsequent stop band is at least two times the bandwidth of the given stop band. In some embodiments of the fourth telecommunication apparatus, each of the stop bands has an order N of at least 6 and a stop band gain that is below −9 dB. In some embodiments of the fourth telecommunication apparatus, the digital filter has between 8 and 20 stop bands.
In some embodiments of the fourth telecommunication apparatus, a size of the regular intervals is user-adjustable. Optionally, in these embodiments, each of the stop bands may have the same bandwidth B, where B is user-adjustable.
Some embodiments of the fourth telecommunication further comprise the speaker. Some embodiments of the fourth telecommunication further comprise a microphone that generates the microphone output signal.
Various embodiments are described in detail below with reference to the accompanying drawings, wherein like reference numerals represent like elements.
The digital filter 30 implements m band-stop filters BSF1, BSF2, . . . BSFm connected in series, where m is at least 4.
Experimental testing revealed that filtering using the particular set of parameters identified in the previous paragraph provided improved understandability of speech for most members of a group of test subjects. This experimental testing was accomplished using digital signal processing algorithm software running on a personal computer (PC) to implement a set of m band-stop filters arranged in series, with the center frequencies of all the stop bands positioned at regular intervals on a linear scale. The software was programmed to vary m, the bandwidth B of the stop bands, the spacing between the center frequencies of the stop bands, the gain in the stop bands, and the order N of each of the band-stop filters based on inputs received from users via a user interface.
In the experiments, a group of individuals with relevant hearing impairments listened to a recording of a clean speech to which noise was added. The added noise was “cocktail party” type noise, which is a background noise that one would encounter in busy public places such as a busy restaurant, and
The signal to noise ratio (SNR) was controllable. After the SNR was set to a value at which a given test subject could not understand the speech when the digital filter was turned off, The test subjects were given access to a GUI similar to the one depicted in
Sets of parameters for the digital filter that provided improved ability to understand speech were found within the following ranges: filter order N of at least six; number of band-stop filters m between 8 and 20; and stopband gain below −9 dB.
By way of comparison, when the GUI depicted in
Returning to
In alternative embodiments, the system (including components 20-50) is miniaturized to the size of a hearing aid that rests on or in the user's ear, and the digital filtering algorithms described above are implemented by a digital signal processor (DSP) chip incorporated within the miniaturized system. In these embodiments, the DSP chip can perform the functions of both the digital filter 30 and the controller 50. Alternatively, the DSP chip can perform the functions of the digital filter 30 only, and a separate integrated circuit can perform the functions of the controller 50. In these miniaturized embodiments, the user interface 60 may be implemented using an app on a smart phone that communicates with the controller 50 using any conventional communication approach (e.g., Bluetooth). Of course, a wide variety of alternative user interfaces 60 can be readily envisioned, including but not limited to a set of dials and/or switches that can be actuated by the user to adjust the parameters of the digital filter 30.
In some embodiments, the entire system depicted in
Optionally, the controller 50 can be programmed to implement a “training mode” to help any given user specify a set of parameters for the digital filter 30 that works best for that user. One suitable approach for implementing this training mode is to program the controller 50 to output an audio signal corresponding to a given set of words (e.g., using a prerecorded audio file or text-to-speech), and to send that audio signal into the digital filter 30 for processing and subsequent output to the user (e.g., via the audio amplifier 40 and the speaker 42). The first time a user uses the system, the user is prompted (e.g., via the user interface 60) to adjust the set of parameters and to indicate when good intelligibility is achieved while the set of words are being output (and, if necessary, repeated). The controller 50 and the user interface 60 may be programmed to accept indications of intelligibility using any of a variety of alternative approaches (including but not limited to pressing a single user interface button to indicate when intelligibility is good, ranking intelligibility on a scale of 1-10, etc.). The controller 50 saves the parameters that correspond to good intelligibility in memory for subsequent retrieval.
Optionally, noise may be added to the audio signal corresponding to the given set of words while the given set of words is being output to the user during the training mode, and the level of the noise (with respect to the signal) may be user-adjustable. Optionally, the controller 50 may be programmed to give the user the ability to repeat the training mode on demand.
Whenever the system is subsequently used, the digital filter 30 uses the stored set of parameters when processing incoming audio data. More specifically, the system will input incoming audio signals, filter those incoming audio signals using the digital filter 30 using the stored set of parameters, and output a filtered version of the incoming audio signals.
In some embodiments, the user interface 60 allows the user to control all of the parameters described above. (See, e.g., the GUI 62 depicted in
In other embodiments, use of the user interface 60 is restricted to a practitioner (e.g. an audiologist), and the user interface 60 is not provided to the end-user. In these embodiments, the audiologist could set the parameters for the digital filter 30 during an office visit, and those parameters would remain in force until such time that they are updated by the audiologist. In still other embodiments, after a suitable set of parameters for the digital filter 30 has been identified, those parameters could be hardcoded into a dedicated digital filter, in which case the controller 50 can be omitted from the device that is worn by the user.
Note that in the examples noted above, the center frequencies of all the band-stop filters were positioned at regular intervals on a linear scale. But in alternative embodiments, the center frequencies of all the band-stop filters could be positioned at regular intervals on a logarithmic scale or at irregular intervals.
The results described herein may seem counterintuitive because filtering the signal+noise using a set of at least four band-stop filters arranged in series discards a significant portion of the signal, and because the noise is not arriving at a known frequency. For example, when the digital filter parameters described above in connection with
Without being bound or limited by this theory, one possible explanation of why introducing a plurality of stop bands to the frequency response that arrives at the user's ears improves the user's ability to understand speech in noisy environments is as follows.
Sound sensation is based on the vibration induced by sound waves in the structures of the inner ear (e.g., the cochlea). The hair cells residing on the vibrating base membrane are responsible for the actual transduction of the mechanical pressure waves into neural signals. The amplitude of base membrane response is a function of the sound wave frequency (in the audio range) in a unique way: the response is location selective, i.e. the response at the basal part of the membrane is limited mostly to high frequencies and the responsiveness to low frequencies increases with distance from the base as seen in
The net effect is a bell-shaped response vs. frequency curve (tuning curve), that is somewhat asymmetric, as illustrated schematically in
A similar approach of using at least four band-stop filters may also be applied in the context of a cellular phone.
To understand these embodiments, it will be helpful to first review the operation of a conventional prior art cellular phone.
Incoming communications, on the other hand, are handled differently in the
In some embodiments (referred to herein as option A), the processor/controller 250 is programmed to handle incoming communications in the same way as the processor/controller 150 described above in connection with the
In other embodiments (referred to herein as option B), the processor/controller 250 is programmed to generate the second signal (i.e., the filtered signal) directly from the data that arrives from the transceiver 170 without ever outputting the unfiltered first signal that corresponds to the incoming communications. In these embodiments, the functionality of the processor/controller 250 and the digital filter 230 is preferably combined into a single integrated circuit, in which case the digital filter 230 could be implemented as an object that is executed by the processor/controller 250 (as opposed to a discrete device).
Regardless of whether option A or option B is used, the transceiver 170 receives incoming data, and the processor/controller 250 and the digital filter 230 collectively extract a first signal from the incoming data and process the first signal using a digital filter to generate a corresponding filtered second signal as an output. The digital filter has at least four audio frequency stop bands, with an audio frequency pass band positioned between adjacent stop bands. Each of the stop bands has a respective center frequency and a respective bandwidth, and the center frequencies of all the stop bands are positioned at regular intervals on a linear scale.
Whichever approach is used to generate the second signal (i.e., the filtered signal), the second signal is provided to a digital-to-analog converter 180, which converts the processor/controller's digital output to an analog signal. The analog signal is provided to an audio amplifier 140, which generates an amplified analog version of the second signal that is used to drive the speaker 142. The construction and operation of these components 180, 140, 142 is the same as in the
Optionally, a training mode similar to the training mode discussed above in connection with
While the present invention has been disclosed with reference to certain embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the present invention, as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof.
This application is a continuation-in-part of the U.S. patent application Ser. No. 16/847,978, filed Apr. 14, 2020, which claims the benefit of U.S. Provisional Application 62/836,276, filed Apr. 19, 2019, which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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62836276 | Apr 2019 | US |
Number | Date | Country | |
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Parent | 16847978 | Apr 2020 | US |
Child | 17071587 | US |