Sound

• Sound is made by vibrating objects:-

such as vocal chords, strings, wires, bells.

Echo

• Sound can be reflected off large, hard surfaces and the reflected sound is called an echo.

Sound words

• Amplitude (loudness)

• Frequency (pitch)• Loudness

(decibels)

Waves

• Sound is transmitted as a wave. (longitudinal)

TRANSVERSE WAVE

“an uppy-downy wave”

PEAK

TROUGH

WAVELENGTH AMPLITUDE

LONGITUDUNAL WAVE

“a back and forth wave”

a vibration….

A SOUND WAVE

a BIG amplitude

LOUD SOUND!

a small amplitude

a quiet sound

a small wavelength

a high-pitched sound

a large wavelength

a low-pitched sound

Sound in a vacuum• Sound travels at 330 m/s in air the

vibrations are passed on to the next molecule of air the distance between atoms makes this slow.

• Sound through water s about 1500 m/s. This is because the atoms are closer together.

• The speed of sound in wood is about 4000 m/s the wood is denser and the atoms are closer together.

Pitch = frequency

Hearing range

• Young people can usually hear from 20 Hz to 20,000 Hz, this is from very low pitch (low frequency) to high pitch (high frequency).

• Sound above 20,000 Hz is called Ultrasound.

Range of hearing

Humans can hear up to a frequency of around 20 000 Hz (20 kHz)

11.3 Highs and Lows - Frequency

The number of times an object vibrates every second is the frequency of the sound.

The number of times the strings vibrate every second is the frequency of the sound.

The higher the frequency, the higher the pitch

The lower the frequency,, the lower the pitch.

Often adults may not be able to hear your phone ringing if it has a frequency of over 16000 Hz eventhough young people can as they can hear up to 22000Hz.

More Audible Ranges

Ear protection

• Don’t stay too long in noisy places

• Wear ear muffs/ear plugs if in a noisy place (like using power tools)

• Keep the volume of your music turned down