Limits of Human Hearing

[thadman]

Let us suppose an arbitrary individual, Mary, exists.

We ask Mary to assume a comfortable position in a lovely, leather chair we purchased just for the occasion. We also ask Mary to assume a pair of headphones we borrowed from Zeus, which are perfect in every way imaginable (they're Zeus' headphones).

Let us now suppose that Zeus' headphones (which Mary is borrowing) are connected to a computer which functions as a source. If we sent a signal to Zeus' headphones, Mary perceives this as sound (we assume her ears work).

If we sent Zeus' headphones 2 signals, which possess the same frequency content but different amplitudes, what would be the limit of Mary's hearing where she could no longer differentiate between the two signals?

1dB? .1dB?

[Ron E]

Try it, Mary. ILD perception most likely depends on bandwidth...
http://en.wikipedia.org/wiki/Sound_localization

[thadman]

What is the limit of the human auditory system?

Originally Posted by Master Handbook of Acoustics

The silence presses down on you in the tomblike silence, 10 min-
utes, then a half hour pass. New sounds are discovered, sounds that
come from within your own body. First, the loud pounding of your
heart, still recovering from the novelty of the situation. An hour goes
by. The blood coursing through the vessels becomes audible. At last, if
your ears are keen, your patience is rewarded by a strange hissing
sound between the “ker-bumps” of the heart and the slushing of blood.
What is it? It is the sound of air particles pounding against your
eardrums. The eardrum motion resulting from this hissing sound is
unbelievably small—only 1⁄100of a millionth of a centimeter—or 1⁄10
the diameter of a hydrogen molecule!

How can we quantify this expression?

[SY]

Originally Posted by thadman

How can we quantify this expression?

The usual engineering unit is the RCH.

[thadman]

Originally Posted by SY

The usual engineering unit is the RCH.

[breez]

Originally Posted by thadman

If we sent Zeus' headphones 2 signals, which possess the same frequency content but different amplitudes, what would be the limit of Mary's hearing where she could no longer differentiate between the two signals?

1dB? .1dB?

Depends on signal content. And what is meant by differentiating between the two signals? Usually a single auditory event is heard, but it is displaced from the center of the head towards either side. You could look up lateralization blur which means the smallest change in interaural level difference leading to a lateral displacement of the auditory event.

[pheonix358]

You also need to take into account that our perception of sound is log not linear. Therefore if the noise floor is low you here more subtle sounds. But if your trying to work out if the left turbo prop is louder than the right one, good luck.

Terry

[mscommerce]

1 db

[pheonix358]

Originally Posted by mscommerce

1 db

Can you tell the difference between 145 and 144dB. I can't. It is never so simple. We havn't even talked about the difference between Conceptual Vs Factual brains. They are different.

Terry

[AudioFreak]

The textbook would probably say 1dB but it is highly dependent on the situation. In some very limited situations a very good and well trained set of (human) ears / brain can differentiate between 2 levels less than 1dB apart but in most everyday situations it will probably be closer to 3dB or worse.