# A speaker produces a sound with a frequency of 1000hz. How many waves

1. Jul 18, 2010

### Justin Kirk

A speaker produces a sound with a frequency of 1000hz. How many waves are traveling in the air in front of the speaker? Does the number of waves decrease as one moves away from the speaker? Is there only the single 1000hz wave moving the air in front of the speaker? This is not a homework question, just an idea of how sound may look. I'm trying to picture in my mind a sound wave.

2. Jul 20, 2010

### AJ Bentley

Re: Acoustics

The speed of sound in air is roughly 300 metres per second. So in one second, your speaker produces 1000 waves that occupy the space from zero to 300 metres in front of the speaker. So each wave must be 300/1000 = 30cm long (about a foot).

Of course the waves don't just travel in one direction, they spread out in a sphere from the speaker a bit like a series of rapid blast waves from an explosion, each 1 foot apart.

Does that help?

3. Jul 20, 2010

### Pythagorean

Re: Acoustics

Are you asking what the rate is (number per time)? That would be your 1000Hz. The total number of waves is constantly changing.

It's produce 1000 waves per second, regardless of where you are. The frequency you perceive doesn't change with distance from the source (speaker). Velocity, however, does. If you're moving away from or toward the speaker, you're "moving through" the waves faster or slower, so it's as if the waves were going faster or slower.

1000hz does not represent a single wave. 1000hz means 1000 waves per second. So a series of (ideally) spherical waves just keep on expanding from the stereo, alternating between high and low pressure.