Entry #6

Physics journal 6

Sound part 2

First-- even more terms to remember! (Wait, i think i wrote these down already, but never mind.)

Amplitude: Biggest displacement of particle (From equilibrium position. I.e., its fixed position in the column --> refer to part 1)

Frequency: No. of back and forth vibrations that the particle has. (how many cycles in 1s) 

How to read a sound graph:

On the graph sketched (not very well. ^^'''), is a sample of a wavelength. This kind of curve is called a sine curve. 

As can be seen, the highest point of the sine curve is called the crest, while the lowest point is called the trough. 

How does :

(i) The amplitude affect the loudness?

(ii) The frequency affect the pitch?

Well, 

(i) The lower the amplitude, the softer the sound. (has bigger waveforms)

     The higher the amplitude, the louder the sound. (has smaller waveforms)

(ii) The lower the frequency, the lower the pitch. (has longer waveforms)

      The higher the frequency, the higher the pitch. (has shorter waveforms)

An oscilloscope is used to display waveforms.

Echo

Echo is a reflection of sound. Sound obeys the laws of reflection (i=r)

Sound waves can be reflected by surfaces. Ideal surfaces are smooth, large, upright, and far away. 

A distinct echo can only be heard if the reflecting surface is far enough from the source. If the reflected sound follows very closely, we hear a prolonged sound called reverberation.

To determine the speed of sound, 

Let V be speed, d be distance and t be time.

V=d/t

Period = 1/freq. or freq. = 1/period.

Note: the presence of wind will affect the time taken for sound to travel through air and cause inaccuracies.

Determine the speed of sound by echoes: V=2d/t