# I Sound wave pressures

1. Sep 7, 2017

### physea

Sound waves transmit in atmosphere as dense and thin areas of air. Is there a graph showing the highest and lowest pressure of atmosphere for sound waves of various decibels?

2. Sep 7, 2017

### Staff: Mentor

http://www.acoustic-glossary.co.uk/sound-pressure.htm

the 0-dB sound pressure level (SPL) in air is defined as 2 x 10-5 Pa. This is the root-mean-square difference between the instantaneous pressure and the ambient pressure (the pressure that you would have if there were no sound at all). For other SPLs, you can use the table or the formula given on that page.

3. Sep 7, 2017

### physea

I see 'street traffic' noise pressure is 2 Atm. What does that mean? That pressure the high pressure regions and what the low have in the atmosphere?

4. Sep 7, 2017

### nasu

The pressures are given in Pa and not atmospheres.

5. Sep 7, 2017

### physea

I already know that and I converted them to Atm.

6. Sep 7, 2017

### Staff: Mentor

Check your conversion factor. 0.2 Pa (which the table shows for "street noise") is much much less than 1 atm.

7. Sep 7, 2017

### sophiecentaur

Atmospheric pressure is about 105Pa and traffic noise is about 0.2Pa, which is a tiny fraction of that. I can't think where you got your "2 Atmospheres" from.

8. Sep 7, 2017

### nasu

The pressures in the table are the amplitudes of the pressure variations around the average value (the pressure in the air without sound waves, po).
A value of 2 Pa in the table means that the pressure in the sound wave can be between p0-2Pa and p0+2Pa . Even for the noise so strong that it can damage the ear, the variation are very small compared with the atmospheric pressure.

9. Sep 13, 2017

### physea

I am looking for a graph of the energy we need to produce a sound of x dB with current technology. Any hint?

10. Sep 13, 2017

### sophiecentaur

You would mean Power, not Energy. (Important distinction).
Did you ever try this wiki link?