I'm trying to find a credible source for identifying the approximate number/percentage of human beings who can hear beyond the "normal" range (20 Hz to 20 kHz.). I found many articles offering numbers, but they have no source materials/references to back them up.
From what I've read to date, it seems that people with autism can hear sounds that fall into the ultrasonic range, and younger people can also occasionally hear those normally inaudible sounds. Some people who simply have sensitive hearing (no apparent special conditions and in any age range). But I need a credible source - a research study, data source or scientific organization - that can represent a close approximation of this population size (and make up, if that's possible) is what I need.
e.g. "Approximately 4% of human beings can hear audio signals in the range of 20 -30 kHz.."
Thank you!
Thank you for this link, the site is interesting.
I'll look for published research and data sources. Please forward anything else you know about.
Best regards.
-Infrasound
1. < 20 Hz 2. Earthquake, atmospheric pressure changes, blower in
ventilator 3. Not audible 4. Headaches and physiological
disturbances
- Sound
1. 20 ~ 20,000 Hz 2. Audible
- Ultrasound
1. > 20 kHz 2. Not audible 3. Medical imaging, blood flow
measurements, …etc
Sensitivity of the Ear:
- Not uniform over 20 ~ 20,000 Hz
- Most sensitive range: 2 ~ 5 kHz
- Sensitivity is decreased for old people
1. 45 years old: no perception for over 12 kHz, need 10 dB more at 4 kHz than 20 years old
2. 65 years old: 25 dB loss for > 2 kHz
- Loudness
1. Proportional to the logarithm of intensity
2. Unit: phone, one phone = 1 dB sound at 1000 Hz, 10 phones = 10 dB sound at 1000 Hz
3. Frequency dependent
Think of the fetus in the mother's womb hearing the ultrasound when diagnosis and those who suffer from autism or hearing-related diseases such as hearing loss ... See the book of physics in hearing by author Cameron
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