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[Weogo Reed]

Hi All,

Please help with a subject that has been discussed here before...

Several years ago there was a significant thread about hearing damage, and whether low, mid and high frequencies at the same db level do the same amount of damage.

Can anybody point me to the thread(s), and or good literature on the subject?

I do know about the different perception of frequencies as show by Fletcher~Munson,
and the ISO 2003 hearing curve:
http://en.wikipedia.org/wiki/Equal-loudness_contour

Thanks and good health,  Weogo

[George Friedman-Jimenez]

I remember the thread but could not find it.

The best easily readable literature on hearing loss that I have read is the book "Hearing loss in musicians: Prevention and management" by Marshall Chasin, Plenum Publishing, 2009. It is simply written, comprehensive, up to date, medically accurate, well referenced, and answers most of the important questions for which answers currently exist.

To answer your question briefly, both Temporary Threshold Shift and Permanent Threshold Shift tend to occur approximately a half octave above the offending frequenc(ies). These refer to a shift upward in the loudness of sound necessary to reach the threshold that you can just barely hear it. Normal ears can just barely hear a sound at 0 dB, and if you can't hear it until it reaches 35 dB, for example, that is called a 35 dB threshold shift or 35 dB hearing loss. The shift in threshold can be temporary or permanent. The unprotected ear has a natural resonance in the 2700 - 3000 Hz range, due simply to the length of the outer ear canal. For this reason, much hearing damage tends to occur around this frequency and a half octave above it. This kind of noise-induced hearing loss often is seen on audiograms as a notch in hearing threshold in the 3000 Hz to 6000 Hz range, with relatively more normal hearing at lower and higher frequencies. The threshold graph is plotted with hearing threshold (hearing loss) increasing in the downward direction, vs frequency on the x axis, so a hearing loss around a given frequency looks like a notch. In violinists and piccolo players, the notch can extend up to 8000 Hz. The ear seems to be less susceptible to noise induced hearing loss at lower frequencies, as the great majority of people with NIHL have the greatest hearing loss in the 3k to 6k range.

The book gives good recommendations for prevention of hearing loss, including types of hearing protection to use, but the best recommendation in the book is to avoid mowing your lawn for at least 16-18 hours after a loud concert, to allow your ears to recover from the temporary hearing loss caused by the loud music. Friday and Saturday night gigs should have you covered until the weekdays come, when some of us with day gigs have too tight a schedule to be able to do the lawn after work.

The book is a bit expensive but much cheaper than even a single visit to the ENT doc, and only about 1% of the cost of set of hearing aids.
http://www.pluralpublishing.com/publication_hlim.htm

This free article by the same author has a little bit of the information in the book, but lacks the details: http://www.coordinatemovement.com/articles/HearingLossPreventionForMusicians.pdf

I have not yet read the more recent book by the same author, but it looks good and costs much less. http://www.harriscomm.com/index.php/b1170.html

The Sataloff book is written at a more technical medical level and has more details on hearing loss, but less on music, than the Chasin book:
http://www.crcnetbase.com/isbn/9780824753832

[Weogo Reed]

Hi George,

Thanks for the reply, and I have some books to purchase!

The extra damage around 2700~3000Hz, and extending up to around 6000Hz, based on the focusing effect of the ear canal, makes sense.


Here's my original question stated slightly differently:

Is eight hours of 100db at 50Hz as damaging as eight hours of 100db at 500Hz?

Thanks and good health,  Weogo

I remember the thread but could not find it.

The best easily readable literature on hearing loss that I have read is the book "Hearing loss in musicians: Prevention and management" by Marshall Chasin, Plenum Publishing, 2009. It is simply written, comprehensive, up to date, medically accurate, well referenced, and answers most of the important questions for which answers currently exist.

To answer your question briefly, both Temporary Threshold Shift and Permanent Threshold Shift tend to occur approximately a half octave above the offending frequenc(ies). These refer to a shift upward in the loudness of sound necessary to reach the threshold that you can just barely hear it. Normal ears can just barely hear a sound at 0 dB, and if you can't hear it until it reaches 35 dB, for example, that is called a 35 dB threshold shift or 35 dB hearing loss. The shift in threshold can be temporary or permanent. The unprotected ear has a natural resonance in the 2700 - 3000 Hz range, due simply to the length of the outer ear canal. For this reason, much hearing damage tends to occur around this frequency and a half octave above it. This kind of noise-induced hearing loss often is seen on audiograms as a notch in hearing threshold in the 3000 Hz to 6000 Hz range, with relatively more normal hearing at lower and higher frequencies. The threshold graph is plotted with hearing threshold (hearing loss) increasing in the downward direction, vs frequency on the x axis, so a hearing loss around a given frequency looks like a notch. In violinists and piccolo players, the notch can extend up to 8000 Hz. The ear seems to be less susceptible to noise induced hearing loss at lower frequencies, as the great majority of people with NIHL have the greatest hearing loss in the 3k to 6k range.

The book gives good recommendations for prevention of hearing loss, including types of hearing protection to use, but the best recommendation in the book is to avoid mowing your lawn for at least 16-18 hours after a loud concert, to allow your ears to recover from the temporary hearing loss caused by the loud music. Friday and Saturday night gigs should have you covered until the weekdays come, when some of us with day gigs have too tight a schedule to be able to do the lawn after work.

The book is a bit expensive but much cheaper than even a single visit to the ENT doc, and only about 1% of the cost of set of hearing aids.
http://www.pluralpublishing.com/publication_hlim.htm

This free article by the same author has a little bit of the information in the book, but lacks the details: http://www.coordinatemovement.com/articles/HearingLossPreventionForMusicians.pdf

I have not yet read the more recent book by the same author, but it looks good and costs much less. http://www.harriscomm.com/index.php/b1170.html

The Sataloff book is written at a more technical medical level and has more details on hearing loss, but less on music, than the Chasin book:
http://www.crcnetbase.com/isbn/9780824753832

[Elliot Thompson]

Hi George,

Thanks for the reply, and I have some books to purchase!

The extra damage around 2700~3000Hz, and extending up to around 6000Hz, based on the focusing effect of the ear canal, makes sense.


Here's my original question stated slightly differently:

Is eight hours of 100db at 50Hz as damaging as eight hours of 100db at 500Hz?

Thanks and good health,  Weogo

Hi.

Wouldn’t the perception of one’s hearing contribute to what he or she finds irritating at high sound pressure levels in terms of frequencies?

There are only two frequencies that I find physically irritating under narrow Q conditions. The first one is 2.5 ( D Sharp 7 ) kHz and, the second is 17 kHz (C Sharp 10 ).
 

Best Regards,

Elliot.

[Jamin Lynch]

I guess we are refering to live sound? In what type application would you have one without the other?

[Elliot Thompson]

I guess we are refering to live sound? In what type application would you have one without the other?

It is more to wards those who are losing their hearing that boost the high frequencies excessively.

Best Regards,

Elliot.

[Dan Richardson]

I guess we are refering to live sound? In what type application would you have one without the other?

Bluegrass on the one hand, dubstep on the other.

[George Friedman-Jimenez]

The extra damage around 2700~3000Hz, and extending up to around 6000Hz, based on the focusing effect of the ear canal, makes sense.

Here's my original question stated slightly differently:
Is eight hours of 100db at 50Hz as damaging as eight hours of 100db at 500Hz?

Weogo, regarding your first statement, it is not just focusing, the external ear canal is a tube about an inch (2.5 cm) long that actually has a resonant frequency somewhere in the 2700 - 3500 Hz range for most people. You can calculate the resonant frequency as f = c/4L where c is the speed of sound in air = 34,000 cm/sec and L is the length of the tube, approximately 2.5 cm for some people. So for those numbers, f=34,000/(4*2.5) = 3,400 Hz. The geometry is not a simple cylindrical tube, there are harmonics involved as well, and the width of the resonant frequency range is broader than a single frequency spike, but a gain of approx 15 dB has been measured for the resonant frequency of a human external auditory canal, compared with frequencies below 400 Hz and above 9000 Hz. You can think of the ear canal as a natural acoustic bandpass amplifier with a center frequency around 3000 Hz and a gain of around 15 dB.

Elliot, I would think the lower frequency, 2,500 Hz, that you find irritating probably represents the natural resonant frequency of your external auditory canal, and possibly some early hearing damage. People with damage to their hearing sometimes become more aware of certain frequencies at high SPLs, while still having an increased threshold of perception at those same frequencies. Or it could be purely perception. As I recommend for nearly all people in the music or sound business, I would suggest getting your hearing tested by an audiologist. At a very minimum, a baseline audiogram when beginning in this industry, then regular follow-up audiograms every few years, will help you identify hearing loss relatively early so you can take more aggressive preventive measures. In addition, audiograms in between the regular screening audiograms, when you perceive a problem with your hearing can be useful. These recommendations are probably too conservative, since evidence of hearing loss on an audiogram often indicates that permanent hearing damage has already occurred. For this reason, some audiologists recommend more sensitive screening tests like otoacoustic emissions testing, which can identify early effects of overexposure to loud sounds before permanent damage occurs.

Weogo, regarding your question, I don't think good research has been done to get frequency-specific estimates of risk of hearing damage from 50 Hz vs 500 Hz sound. Certainly you should never expose yourself for 8 hours a day to 100 dB SPL at either frequency without hearing protection.  Both 50 Hz and 500 Hz are far from the resonant frequency center, so the acoustic bandpass amplifier effect would not be significant in either case. Certainly, however, 100 dB at 500 Hz would sound much louder than 100 dB at 50 Hz, as shown in the equal loudness contours you cited. You would perceive your 100 dB SPL 500 Hz sound as 100 phons, but you perceive a 100 dB SPL 50 Hz sound as around 77 phons, according to that curve. As musicians and SR professionals, our natural reaction to this psychoacoustic effect is to crank up the bass until it sounds roughly as loud as the mids and highs (or even louder in some cases). So in real life with serious subwoofers and a real live DJ spinning and EQing the music, the actual dB SPL at 50 Hz would likely be EQed up to 100 phons to sound about as loud as the 100 phons at 500 Hz. This would be equivalent to a 50 Hz SPL of about 113 dB, to match the 500 Hz SPL of about 100 dB. We don't have enough research to tell us whether the 50 Hz 113 dB sound would be more likely to damage hearing than the 500 Hz 100 dB sound. The OSHA regulations and NIOSH recommendations and dB / time equivalencies sidestep this question by using A weighting and ignoring very low frequencies. They probably err on the side of not being protective enough, rather than being overprotective.

So my recommendation, which I follow religiously myself, is to bring hearing protection whenever you go into a place with music or sound over about 90 dBC for more than an hour. I actually bring an SPL meter to gigs, and have even been known to bring it to parties. You don't have to be that nerdy, you can learn to recognize sounds over about 90 dB without a meter. I have a very low threshold for putting my in ear hearing protectors in. The need to converse or to play music in tune and in time sometimes causes me to take them out even if the sound is too loud, but I usually keep them in most of the night.

[Elliot Thompson]

Elliot, I would think the lower frequency, 2,500 Hz, that you find irritating probably represents the natural resonant frequency of your external auditory canal, and possibly some early hearing damage. People with damage to their hearing sometimes become more aware of certain frequencies at high SPLs, while still having an increased threshold of perception at those same frequencies. Or it could be purely perception. As I recommend for nearly all people in the music or sound business, I would suggest getting your hearing tested by an audiologist. At a very minimum, a baseline audiogram when beginning in this industry, then regular follow-up audiograms every few years, will help you identify hearing loss relatively early so you can take more aggressive preventive measures. In addition, audiograms in between the regular screening audiograms, when you perceive a problem with your hearing can be useful. These recommendations are probably too conservative, since evidence of hearing loss on an audiogram often indicates that permanent hearing damage has already occurred. For this reason, some audiologists recommend more sensitive screening tests like otoacoustic emissions testing, which can identify early effects of overexposure to loud sounds before permanent damage occurs.

Hello George.

I’ve discovered my dislike of 2.5 kHz ever since I was 13 so, I would imagine if this was indeed an early incarnation of hearing damage my hearing would not be able to detect 20 kHz at 31 much less be irritated by 17 kHz (17739.689 kHz ).


Due to how high frequency passes through air under various climates, I am more susceptible to such symptoms in the winter than the summer. I will definitely pay another visit to my doctor and ask her if she can recommend an audiologist.

Thank you for sharing your thoughts.

Best Regards,

Elliot.

[Stu McDoniel]

Hi All,

Please help with a subject that has been discussed here before...

Several years ago there was a significant thread about hearing damage, and whether low, mid and high frequencies at the same db level do the same amount of damage.

Can anybody point me to the thread(s), and or good literature on the subject?

I do know about the different perception of frequencies as show by Fletcher~Munson,
and the ISO 2003 hearing curve:
http://en.wikipedia.org/wiki/Equal-loudness_contour

Thanks and good health,  Weogo

I believe around 2k is where the ear is really really dam sensitive and yea 2.5khz is
annoying to every human on the planet.   That is the region the old paramectric grabs first thing
with me.   If you can make a narrow dip at that freq you really can change the annoyance factor of a soundsystem in a huge way. 

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