An Open Letter to Hard of Hearing Musicians
By Marshall Chasin On April 19, 2016
This letter is based on my 35 years of working with hard of hearing musicians at the Musicians’ Clinics of Canada. Over the past few years an assortment of new technologies for hearing aids have become available that will allow hard of hearing audiophiles and musicians to reprogram their hearing aids once they leave the audiologist’s office. While on the surface this appears to be a good idea- one can fine tune the hearing aids in real life situations with real life musical instruments- there can be some drawbacks.
Recently the tools that audiologists use to program hearing aids have been made available for purchase by anyone. These include the fitting software for any number of hearing aid manufacturers, the interface box between the computer and the hearing aid called HI-PRO, and the necessary wires and cables that can connect the HI-PRO interface to the hearing aids. These can be expensive, but given the cost of many hearing aids, these tools pale in comparison on a cost basis to the hearing aid expenditure. Of course the cost is for much more than the physical hearing aid. It consists of prescribing the correct amount of (possibly level dependent) gain and limits of the frequency response, follow-up, and most importantly the verification that the hearing aid actually does what it is supposed to do.
The short story is that I recommend that you leave the programming and verification in the hands of the audiologist. While this last statement sounds paternalistic, let me give you the longer story to explain why this is actually for your own protection.
There are many hearing aid parameters that need to be adjusted and verified by the audiologist. To be fair, most of these parameters are rather benign and the worst case scenario is for you to reset them to the initial settings. These may include the frequency response, the various features of the compressors (including kneepoint thresholds, attack and release time, and compression ratio). These parameters are probably well known to musicians and audiophiles. Many use software for music composition and recording that has all of these parameters such as Logic Pro. I would suspect that the experienced musician probably knows as much about these parameters, especially for music, than many audiologists.
The one parameter that can cause additional permanent hearing loss (also found in the LogiPro and other music software) is the maximum sound that can be transduced through hearing aids. Audiologists refer to this as the OSPL90, or maximum Output Sound Pressure Level with 90 dB SPL input. If the OSPL90 is set too high, then permanent future hearing loss can occur.
This is where the audiologist comes in, armed with Boyle’s Law.
Boyle’s Law is a 17th century discovery made at Imperial College in London, England. Boyle found that in an enclosed volume the pressure was inversely related to the volume- the smaller the volume, the higher the pressure, and this includes the sound pressure as well. We learn this in high school chemistry classes as part of the ideal gas law. This is also why balloons tend to explode when one sits on them- the volume is decreased to a point where the pressure is so great that the balloon explodes.
The maximum output or OSPL90 that will be seen on the hearing aid fitting software is a number measured in a 2 cc coupler. That number is fairly accurate if your ear canal with a hearing aid in place has a volume of 2 cc but we rarely see that “average person”. People with smaller volume ear canals such as children, have a much greater sound level generated at their eardrums than what the OSPL90 number will indicate. This can easily be as much as a 10-15 dB difference, depending on the frequency.
Of the many tests that an audiologist uses to verify hearing aid function, there is a device called a probe tube microphone measurement. As the name implies this is a controlled miniature microphone situated at the end of a long silicon tube that can measure precisely what the hearing aid generates. Without verifying the sound levels in a person’s ear one cannot be sure that the sound levels are too great.
In the near future, other technologies will be coming onto the market that again, will allow the hard of hearing audiophile or musician to program their own hearing aids. If you are so predisposed, go ahead and experiment with the frequency response, and compression characteristics, but also make an appointment with your local audiologist to have them ensure that the set-up does not generate sound levels that are too great.
Audiologists can verify that this is the case, and can even provide you with a frequency-by-frequency correction/calibration curve that translates the numbers on the computer screen to actual sound levels that can be generated in your ear canals.
- The views and opinions expressed in posts do not necessarily state or reflect those of Hearing Health and Technology Matters, LLC. Copyright © Hearing Health & Technology Matters, LLC. 2017. All rights reserved. Originally posted April 19, 2016. Reposted with permission on the Hearing Aids For Music website on October 4, 2017.
A musician’s wish list for his hearing aids
By Rick Ledbetter, December 27, 2016
Rick Ledbetter is a long time professional bass player and composer with a profound, late onset hearing loss. He has been programming his own aids through several sets, to meet his needs for live performance. Rick is quite thoughtful about this area. In April 2016 I had an open letter to hard of hearing musicians, which was repeated last week during the holiday season break, and what better response than this wish list for audiologists and hearing aid manufacturers…(Marshall Chasin).
Musicians have picky ears, from years of critical listening and learning what musical instruments should sound like, both solo and in ensemble. We can listen to an ensemble play, and pick out what one instrument is doing while the music is being played. So, to do that with hearing aids, we need aids that reproduce sound with the greatest fidelity and real world frequency response at all volume levels, but particularly from 65dB to over 100dB, to handle the brief peaks that even an orchestra can produce.
Hearing aids have long been considered as speech amplification devices, and the programming reflects that: lack of clean low end, a reliance on sound modifiers like speech enhancers, noise reduction, directionality, etc., to make speech more intelligible in day to day life. However, these same active sound modifiers work against fidelity in live music situations. Feedback reducers don’t know the difference between feedback and a flute, a sustained violin, and an electric guitar high note. Noise reducers don’t know the difference between noise and a drum set, with cymbals. And automatic program switchers go nearly berserk in the presence of live music, especially music that has a wide dynamic range. Musicians can hear this.
In my experience, there isn’t much consideration given to fidelity at the dynamic range of live music, particularly at louder levels. MPOs set too aggressively will serve to squash the sound and bury the sonic detail of the music. What I have found with the aids I have had, is too much amplification at the 80 dB EQ curve, especially from 500 Hz to 2 kHz, and too much limiting from the MPOs. So the volume gets loud too quickly, then limited too soon by the MPOs.
Typical ways to try to address this have been to create a single EQ band “Music” program, with little to no sound modifiers. But that doesn’t allow enough dynamic range, and under -amplifies at lower volume levels. The solution usually offered is to change aid programs, but a performing musician doesn’t have the time to do that, number one, and most aids will temporarily mute and chime when switching programs, which is huge “no no”. We need to hear all the time, and we also don’t have time to be fumbling with buttons on the aids or on the cell phone hearing aid app to change programs. We need both hands to play our instrument, so whatever program is used, it has to work for both live music and conversation.
Then there is a matter of EQ placement points. Over half of a piano is under 500 Hz. And more than half of musical instruments have their tonal characteristics down there, too. An electric guitar is mostly from 250 Hz/ 500 Hz, then all the way up to 6 kHz. Electric bass is from 32 Hz (low B) up, with the overtones in the 125 to 600 Hz range. Saxophones are mostly around 500 / 750 Hz and up. So it is critical for musicians to have even response from 750 Hz down. But hearing aids generally have 3 EQ points in that range. So, when a musician needs low end, and there is only a 250 Hz EQ to do that, too much gain in that region can risk occlusion, also known as “mud” and “boom” to a musician.
Musicians cannot be subject to the “try this and come back in two weeks” fitting process. We need our aids to be right, from the beginning, or at least 80% there. The pre-programming formulas are not right for the demands of live music, and the audiologist often doesn’t have the sound gear to create real world level music in the clinic with real world sound samples. An important point there is that 99% of recorded music is compressed, reducing the dynamic range.
Add to that, expecting high end computer speakers to do the fitting job doesn’t work. The in situ and RTA tests are helpful, but, at least for me, the results of the adjustments from in situ and a RTA machine have never worked above 70 dB SPL.
Then finally, there is the communication barrier. I know it’s frustrating to an audiologist when the patient says, “too loud” but what they need is “less 500 Hz at 80dB SPL”. So imagine what it is like when the musician patient says, “the tenor saxes in their mid-range are too blatty and the sound there is so muddy that I can’t tell the difference between the tenors and trumpets on stage”.
To an audio engineer, this would mean that this is probably a 750 Hz issue. But if the audiologist doesn’t have the same frame of reference, then what the musician says isn’t understood, and it becomes a case of frustration on both sides.
So I would like to propose a wish list for musicians, to address these points:
- Get the initial programming as close to “right” from the very first.
- Redefine what a proper “Music” program should be, to address the demands of live music, at real world volume levels. This would have no signal processing / sound enhancers at all, just EQ-ing and the maximum outputs properly set. In my experience, I have had better success by spreading out the three EQ curves, and using WRDC, and a couple of other basic settings.
- Addition of EQ bands at the sub 500 Hz, at least one at 125 Hz, which some aids have, but others do not. I know some hearing aid manufacturers have relocated the EQ points to reflect the demands of music, which is a great step forward. What would be helpful would be to add in two sweepable narrow range parametric EQ points that can notch out those problematical in-between -spots.
- Spend more time dialing in better fidelity at louder volume levels.
- For hearing aids that use a cell phone app as a remote controller, add in more EQ adjustment points, besides just bass and treble. Possibly put a sweepable parametric EQ instead. Then give the audiologist the ability to download the data from the phone for in clinic modifications to the settings.
- Allow an option for the hearing aid to change programs without notification and without muting. I rely on my cell phone app to change programs, so I can see what program I’m on there.
- Increase the headroom and fidelity on the input stage and output stage of the hearing aid, both with the hardware and the hearing aid’s processor and programming.
Many of the needs of performing musicians overlap with those of other aids wearers. While we have better critical listening skills and more demands on our aids, some of the basic issues, like reducing the number of fitting sessions with more accurate initial programming, still apply to everyone who wears an aid.
- The views and opinions expressed in posts do not necessarily state or reflect those of Hearing Health and Technology Matters, LLC. Copyright © Hearing Health & Technology Matters, LLC. 2017. All rights reserved. Permission granted for use. Originally posted on December 27, 2016. Reposted with permission on the Hearing Aids For Music website on October 4, 2017.