An audio signal (including beep ) is an electrical signal that conveys audio information. On many devices, consumer electronics, the term audio signal is also used to distinguish from the video signal.

The processing of audio signals and the conversion between sound and audio ( microphone signal) are the subject of sound engineering and signal processing.

  • 3.1 harmonic complex tones
  • 3.2 Approximated harmonic complex tones
  • 3.3 Low harmonic complex tones

Frequency range

The frequency range of audio signals is often inspired by the human ear and therefore ranges from about 20 Hz to 20 kHz (low frequency). To exclude audible interference of the signal near the two boundary frequencies for the highest requirements in the hi-fi and studio equipment as well as general applications (eg animal imaging, ultrasound ) devices and storage media (eg, Super Audio CD, DVD-Audio) with considerably further frequency range used.


  • Signals from cassette tapes: typically 50 Hz to 12 kHz
  • Signals of professional tapes: 15 Hz to 18 kHz
  • Theoretical bandwidth of the Compact Disc: 0 Hz to 22.05 kHz
  • Theoretical bandwidth of the SACD: 0 Hz to 48 kHz
  • Signal easier mics: 35 Hz to 15 kHz
  • Signal of good studio condenser microphones: 5 Hz to 22 kHz
  • Usable range of studio microphones measuring 3 Hz to 45 kHz
  • Range of good hi-fi amplifiers: 10 Hz - 30 kHz
  • Range of good studio amplifiers: 5 Hz - 40 kHz
  • Bandwidth of ultrasonic microphones: typically 1 kHz - 150 kHz

For digital audio signals, the audio signals are transmitted and processed as numerical values ​​, the sampling rate determines how many such numbers per second are recorded and processed. Digital audio signals have depending on the audio format and number of channels in some cases Bandwidths up to 10 MHz.

Signal strength

The strength of the audio signal is generally referred to as levels. For analogue audio signals, the signal level corresponding directly to the amplitude of the electric voltage, which is in turn proportional to the sound pressure and the particle velocity.

For digital audio signals of the technical signal level is independent of the volume and is determined by the data transfer device.

Types of sound

According to the psychoacoustics are sounds of speech and music in most cases complex sounds, so sound signals that can be described as the sum of a finite number of sinusoidal partials. One can take three broad distinctions.

  • Harmonic complex tones
  • Approximated harmonic complex tones
  • Low harmonic complex tones

Harmonic complex tones

A distinction between purely harmonic and inharmonic complex tones is practically the basis of physical criteria hardly or only with a certain probability possible. Generally referred to as harmonic complex tones those which are periodic and corresponds to the root of the main perceived pitch. The second criterion can be verified by auditory pitch compared with pure tones. These complex tones include almost all sounds, voices and language physically generated.

Approximated harmonic complex tones

As approximated harmonic complex tones shall refer to such designated, the higher frequency components are in an exactly integer reference to the fundamental frequency, and already have a non -negligible proportion of inharmonicity.

Low harmonic complex tones

As low harmonic complex tones sound signals are known to differ significantly from their Teiltonfrequenzen harmonic pattern. This includes all the sounds which are produced by striking of bells, rods or tubes or membraneartigen bodies. Common musical instruments of this kind are glockenspiel, xylophone, marimba, timpani and drums. The frequencies of the natural vibrations of bells, plates, rods or membranes are not a priori to each other in a harmonious relationship and must be brought through specific working and shaping until approximately harmonious relationship.

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