1Seeing sound
A microphone connected to an oscilloscope shows a sound as a wave on a screen, called a trace. The trace is a graph of the vibrations: sound itself is still longitudinal.
oscilloscopetrace
Lesson 9.3 notes
Loudness, pitch and hearing ranges
Oscilloscope traces, amplitude and loudness, frequency and pitch, and what humans and animals can hear.
2Loudness
A louder sound has a bigger amplitude: its trace is taller. The vibrating object moves further each way.
amplitude
3Pitch
A higher pitch means a higher frequency: more waves fit across the screen. The object vibrates faster.
pitchfrequency
4Hertz
Frequency is measured in hertz (Hz). 1 Hz is one vibration each second. Middle C on a piano is about 260 Hz.
hertz
5Comparing traces
Compare traces made with the same settings. B is taller than A, so it is louder. C has more waves than A, so it has a higher pitch.
6Hearing ranges
Humans hear from about 20 Hz to 20 000 Hz. Sound above our range is ultrasound; below it is infrasound. Bats hear ultrasound; elephants hear infrasound.
ultrasoundinfrasound
7Looking after your hearing
As people get older, they stop hearing the highest frequencies. Very loud sounds can damage the tiny hairs in the cochlea for good, so wear ear defenders near loud noise.
Explore: Oscilloscope
Change the loudness and the pitch of a sound and watch its trace change. Press play to hear it.
Common mistake: Pitch is not the same as loudness
A high note can be quiet and a low note can be loud. Loudness depends on the amplitude; pitch depends on the frequency.
Remember
- A bigger amplitude makes a louder sound. A higher frequency makes a higher pitch.
- Frequency is measured in hertz (Hz): the number of vibrations each second.
- Humans hear from about 20 Hz to 20 000 Hz. Sound above this is ultrasound; sound below it is infrasound.
Going further at GCSE
GCSE: Waves revision → GCSE: Transverse and longitudinal waves →