Wavelength
What is wavelength?
The wavelength of a sound wave is the physical distance between two consecutive points of the same phase in the wave, such as from one peak to the next peak, or from one trough to the next trough.
Measuring Amplitude:
Wavelength is typically measured in units of length, such as metres (m) or feet (ft). It can be calculated using the following formula:
λ = v / f
Where:
λ (lambda) = wavelength measured in metres or feet
v = velocity of sound in the medium - in air at 20°C (68°F) approximately 343 metres per second (m/s) or 1,125 feet per second (ft/s)
f = frequency of the sound - measured in Hz
Another important concept related to wavelength is the period (T) of a wave, which is the time it takes for one complete cycle of the wave to pass a fixed point. The period is the reciprocal of frequency:
T = 1/f
Where:
T = period (in seconds)
f = frequency (in Hz)
Example:
For a low frequency sound of 50 Hz: Metric: λ = 343 m/s / 50 Hz = 6.86 m Imperial: λ = 1,125 ft/s / 50 Hz = 22.5 ft
For a mid-range frequency of 1,000 Hz: Metric: λ = 343 m/s / 1,000 Hz = 0.343 m Imperial: λ = 1,125 ft/s / 1,000 Hz = 1.125 ft
For a high frequency sound of 10,000 Hz: Metric: λ = 343 m/s / 10,000 Hz = 0.0343 m Imperial: λ = 1,125 ft/s / 10,000 Hz = 0.1125 ft
These calculations demonstrate that as frequency increases, wavelength decreases, and vice versa.
Figure representing wavelength, amplitude and period on a sine wave.
