The Berlin wall between music and speech – it’s now down!

The Berlin Wall has fallen…. again…. Actually the wall between having hearing aids that can handle speech as well as the more intense components of music has been down for about a decade but for some reason the hearing aid manufacturers have not announced it.

It is true that there are some differences between music and speech.  It is also true that the number of similarities, at least as far as hearing aids are concerned, between music and speech as an input to a hearing aid.  And it is also true that there seems to be a significant amount of resistance by almost everyone involved to designing a hearing aid that is optimal for music.

Hearing aid designers were not talking to hearing aid marketing people; audiologists were not talking to musicians and sound engineers; and even if they were talking, nobody was listening.

Well, in spite of all of this, we have it all figured out.  Maybe the thinking of one group had to catch up to that of another group, or maybe the technology became available that could handle the differences, or …, who knows what?  But the bottom line is now that the hard of hearing consumer who either plays or just likes to listen to music, can now have hearing aids that are distortion free (at least up to an input of 115 dB SPL).    Inputs greater than 115 dB SPL do exist but are limited to Wagnerian operas and acid rock music, which I would argue should never be played! (I bet that I will get some emails over that comment…).

It turns out that there really isn’t as large of a difference between speech as an input to a hearing aid, and music as an input to a hearing aid, as we once thought.  The research of Dr. Brian Moore, and that of Dr. Todd Ricketts has pretty much shown us that the frequency response selections are more of an issue of the configuration and degree of the hearing loss.  Relatively flat hearing losses and those that are not too severe require as broad a bandwidth as a hearing aid can generate- it is irrelevant whether the input is speech or music.  More severe hearing losses and those that have a steeply sloping audiometric configuration require a more limited frequency response- again, it is irrelevant whether the input is speech or music.  This is basic audiology and nothing to do with music or speech.

Compression for a “music program” and a “speech in quiet program” should be identical.  This has been well shown in the literature.  Compression with modern hearing aids is more of an issue of re-establishing normal loudness contours which is a cochlear (inner ear) phenomenon and has nothing to do with whether the input is speech or music.

The big difference between speech and music as an input to hearing aids is ‘simply” the sound level.  Loud speech (80 dB SPL) is equal to soft music.  There is nothing in any language of the world that is as intense as medium or loud music- the most intense component of speech is about 85 dB SPL and that is the low back vowel [a] as in ‘father’.  In contrast, there is very little in the way of music that is as quiet as 85 dB SPL.  This has necessitated an entirely new generation of input hardware for hearing aids that can handle these more intense inputs of music.

The first solution was in the late 1980s with the introduction of the K-AMP.  This analog circuit was, well,… analog- there was no need for an analog-to-digital (A/D) converter.  And with a few other interesting items, the K-AMP was able to handle all inputs (with the exception of Wagnerian operas and acid rock music) with minimal distortion.  To date, this is probably the best designed hearing aid for handling the inputs of music.

All newer technologies that were designed for modern digital hearing aids had to circumvent the problems of the A/D converter which could only handle inputs up to about 96 dB SPL (medium level music).  Ducking under this low hanging bridge and then standing up again is all that is required.  The more intense components of music are reduced before the A/D converter in order to make it more “speech-like” and then re-expanded after the A/D converter which re-establishes the music’s normal input features.

One approach is to use an analog compression before the A/D converter and then use digital amplification after the A/D converter to ensure that the music has not been altered.  Four hearing aid manufacturers now use this technique and one of the manufacturers has just announced this in the last several weeks.  I have listened to these hearing aids and they sound great.   This technology is not new and has been around for more than a decade.

Other technologies have been available for even longer.  This includes the use of a hearing aid microphone that is less sensitive to the intense lower frequency components of music- they are re-established in the hearing aid software but this “low tech” innovation allows the music to duck under the low hanging A/D converter bridge.

Another technology recognizes that this 96 dB limit on modern A/D converters is not really 96 dB SPL but only a 96 dB “range” and they have a hearing aid that passes all sounds from 15 dB SPL to 111 dB SPL- a range that is well suited for music.

In short (or is it too late?) the hearing aid industry has solved the problems of only providing distorted music.  Now it’s our turn to start listening to our clients and provide further feedback (the good type of feedback) to the hearing aid manufacturers.  They do listen if our feedback is meaningful and constructive.

And…. To further increase communication between our clients, the hearing health care professionals and the hearing aid manufacturing industry… see below:

The Association of Adult Musicians with Hearing Loss (AAMHL) is a unique community made of adult musicians with hearing loss, music educators and individuals in the hearing health industry who are interested in music and hearing loss. For our upcoming web conference on listening to and making music with cochlear implants in September 2013, we invite proposals from researchers who are currently engaged in research on how cochlear implants handle aural music input.

A small honorarium will be provided for researchers who are selected to present at our web conference.

Criteria for selection:

1. Presenters must be willing to provide a 30-minute presentation, using NON-technical language, to discuss their research to our community of interested individuals who do not have extensive backgrounds in hearing science.

2. Presenters must be wiling to sign a release allowing AAMHL to keep the power point of their presentation as part of the conference proceedings.

Please send a brief proposal of your presentation and a copy of your CV or resume to: info@aamhl.org

The deadline for proposal submission is March 30, 2013.

About Marshall Chasin

Marshall Chasin, AuD, is a clinical and research audiologist who has a special interest in the prevention of hearing loss for musicians, as well as the treatment of those who have hearing loss. I have other special interests such as clarinet and karate, but those may come out in the blog over time.