Waveforms

A waveform is a graphical representation of a sound wave as it moves through a medium over time.

Any waveform has four fundamental characteristics:

Wavelength
Amplitude
Frequency
Velocity

Remember not to confuse a waveform, which displays a transverse wave, with the true nature of sound. A real soundwave is longitudinal. The waveform which represents the longitudinal wave is usually shown in audio diagrams as a transverse wave to help us visualize the soundwave better.

Wave form example — Figure 1 - Waveform diagram showing the wavelength and amplitude of a soundwave

Wavelength

The wavelength of a wave is the length in meters from the start to the end of one full cycle of the waveform e.g. from crest to crest.

Amplitude

The amplitude is the maximum displacement of a wave from the centerline to the peak, not from peak to peak. The greater the distance from the centerline of a waveform, the more intense the pressure variation will be within a medium, hence the louder it is perceived.

Amplitude is measured in two ways:

Zero to peak value which measures the maximum positive or negative signal level
Root-mean-square (RMS) value measures a more meaningful average level, like that at which humans hear.

Frequency

Frequency is how many complete waves there are per second passing a certain point. The frequency indicates the rate of pressure variations or cycles per second of a wave.

Frequency is measured in Hertz.

The frequency of a sound determines the pitch, the sensation of how low or how high a sound is.

Lower frequency sound waves have longer wavelengths and lower pitch
Higher frequency sound waves have shorter wavelengths and a higher pitch.

Low frequency wave in comparison to a high frequency wave — Figure 2 - Low-frequency wave (top position) in comparison to a high-frequency wave

The frequency range in which humans can hear is 20Hz to 20,000Hz and is called the audible range, or the audio spectrum.

Velocity

The velocity is the speed and direction of a soundwave. Soundwaves travel at different speeds through different mediums. Through the air, sound travels at 344 meters per second.

Generally speaking, the denser the medium the faster sound travels through it.

To find the velocity of a wave the following equation is used:

Velocity (V) = Frequency (f) x Wavelength (λ)

Sound Waves

Sound Envelopes