I am always amazed by how little amplification is required for listening to music. My typical suggestion is that most people with a mild to moderate hearing loss should simply remove their hearing aids as they provide little or no gain for the more intense components of music. And as a general rule, when listening to, or playing live music, this is probably correct.
Most hearing aids distort with inputs in excess of 95 dB SPL and this has nothing to do with the processing or the cost of the hearing aid and has everything to do with the analog to digital converter (and a 16 bit hearing aid). These “front end” devices are found in all digital hearing aids and with the exception of four innovations that are on the market place today, are severe limitations for listening to high fidelity, distortion free music. And oh yes, the four innovations are the K-AMP (that has no analog to digital converter); all hearing aids with the HRX circuit (initially from Gennum, then purchased by Sound Design, and most recently purchased by ON Semi-conductors), those with a low cut microphone (-6 dB/octave), and those with a front end that can auto-range from 15-111 dB SPL rather than the 0-96 dB SPL found in most other 16 bit systems), but those comments are from previous blogs so I won’t dwell on that.
Today, I would like to dwell on gain corrections for music versus that of speech.
Soft speech, average speech, and loud speech are typically taken to have inputs of 55 dB, 65 dB and 80 dB SPL but this does vary from manufacturer to manufacturer and from fitting algorithm to fitting algorithm. Although we are not sure exactly which numbers to use for soft, average, and loud speech suffice it to say that the most intense components of speech are on the order of 80 – 85 dB SPL. It turns out that loud speech is comfortably average music- everything is shifted up by about 15 dB for the analogous range for music.
The following chart is derived from Fig-6 but almost identical data could also have been derived from the latest versions of the NAL and DSL fitting formulae. The table shows the amount of gain for a range of hearing losses in dB HL at 1000 Hz for very soft music (65 dB input); comfortable music (80 dB input); and comfortably loud music (95 dB input). Even people with a hearing loss of 85 dB HL at 1000 Hz may only need 4 dB of gain for comfortably loud music.
dB HL at 1000 Hz 65 dB input 80 dB input 95 dB input
|
15 |
0 |
0 |
0 |
|
25 |
2 |
1 |
0 |
|
35 |
8 |
4 |
0 |
|
45 |
14 |
7 |
0 |
|
55 |
20 |
10 |
1 |
|
65 |
28 |
15 |
2 |
|
75 |
36 |
20 |
3 |
|
85 |
44 |
24 |
4 |
While the 65 dB input (very soft music and average conversational speech) are well defined by NAL and DSL, the 95 dB input (comfortably loud music) is not typically considered by most audiologists. Even for severe hearing losses only several decibels of amplification is required.
So… my general clinical rule: “Most people with a mild to moderate hearing loss should simply remove their hearing aids when listening to live music” is probably quite true.
