Characteristics of sound waves

6.05

What are sound waves caused by?

Vibrations

For example: the rapid, backwards-and forwards oscillations of a loudspeaker cone

What happens is a pitch of a note is increased by one octave?

The frequency doubles.

What is the range that the human ear can detect frequencies?

20 Hz-20000 Hz

The ability to hear high frequencies will decrease with age

How many Hz is 1 kilohertz (kHz)?

1000 Hz = 1 kHz

the diagrams show what happens if two steady notes, an octave apart, are picked up by a microphone and displayed on the screen of an oscilloscope. Explain the difference in waveform.

The higher note has double the frequency of the lower note, the peaks occur twice as often and are only half as far apart.

The sound waves displayed on the oscilloscope screens above have the same frequency, but one is louder than the other. Explain the difference in oscillations and the amplitude of the waveform.

The one that is louder has bigger oscillations in the air, and the amplitude of the waveform is greater.

What happens if the amplitude of a sound wave is doubled?

Sound waves carry energy. Doubling the time means that four times as much energy is delivered per second.

Middle C on a guitar does not sound the same as middle C on a piano, and its waveform looks different. Why is that?

Because the two sound have a different quality or timbre (tone quality).

Each sound has a strong fundamental frequency, giving middle C. But other weaker frequencies are mixed in as well. these are called overtones, and the differ from one instrument to another.