Loudness and Pitch

It is possible to convert a sound wave into an electrical signal, which allows its waveform to be studied using an oscilloscope.

Although sound waves are longitudinal, oscilloscopes display them as if they were transverse waves. Let’s look at a basic wave diagram and wave properties:

Amplitude – The distance between the midpoint and the peak of the wave, or the midpoint and the trough of the wave. A wave’s amplitude indicates how loud the sound is. The greater the amplitude, the louder the sound is.

Frequency – The number of complete waves that go past a given point per second. A wave’s frequency indicates the sound’s pitch. The higher the frequency, the higher the pitch. Frequency is measured in hertz (Hz).

Wavelength – The distance between two peaks, which are next to each other or any two identical points which are next to each other. In the basic wave diagram above, the wavelength is measured at the midpoint, not the peak.

Frequency and wavelength are inversely related; the shorter the wavelength is, the higher the frequency will be.

Human hearing

We hear sound using our ears, as the sound makes our eardrum vibrate. Microphones contain a diaphragm, which works in a similar way to our eardrums. When sound vibrates in the air, it causes the diaphragm to vibrate, converting these vibrations into electrical impulses.

Humans can hear a wide range of frequencies, but we can’t hear everything.

The range of frequencies humans can usually hear is between 20 Hz and 20,000 Hz (20kHz).

  • Sounds above 20,000 Hz are called ultrasound
  • Sounds below 20 Hz are called infrasound

Here is a table showing the hearing ranges (in Hz) for various species:

SpeciesHearing range (Hz)
Bats20 – 120,000
Dogs67 – 45,000
Elephants16 – 12,000

Some animals can hear in the ultrasound range (above 20,000 Hz), such as bats.

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