# Air Pressure and Sound?

1. Nov 18, 2009

### T.O.E Dream

Is the air pressure near an object making lots of noise (e.g. engine, speaker) higher than the air around it?

2. Nov 18, 2009

### Staff: Mentor

In total no. Sound is air pressure fluctuations, but a sound wave includes an up and a down.

3. Nov 19, 2009

### Archosaur

Going further, though, the fluctuations are more dramatic near the object, meaning it will have the highest highs, but again, equaly low lows.

4. Nov 19, 2009

### T.O.E Dream

If I understand it right sound means that the air pressure increases then decreases and so on? Is the more dramatic the fluctuations the louder the sound?

5. Nov 19, 2009

### T.O.E Dream

In other words if I had a device that measures air pressure it should be going up and down and up and down. And the further it goes up and down the louder the sound?

6. Nov 19, 2009

### DaveC426913

Yes. The amplitude of the wave is directly resultant in the volume of the sound.

You could label this diagram with air pressure notches up the Y-axis:
- 0 air pressure at the origin (lower left corner) of the graph
- low air pressure up the y-axis to the x-axis
- ambient air pressure at the x-axis
- high air pressure up the y-axis off the chart

The diagram represents a sound steadily increasing in volume from left to right.

Last edited: Nov 19, 2009
7. Nov 19, 2009

### T.O.E Dream

And how does insulation lower the intensity of these fluctuations (i.e. lower the volume of the sound)?

8. Nov 19, 2009

### DaveC426913

Is this homework?

How do you think insulation affects the sound?

9. Nov 19, 2009

### T.O.E Dream

I'm wondering something about active noise control headphones. It says that the amplitude must be the same for the sounds to cancel out, does that mean the volume (or loudness) of the sound must be the same?

10. Nov 19, 2009

Yes.