Audio signal
An audio signal (also a sound signal ) is an electrical signal that carries acoustic information. In many entertainment electronics devices , the term audio signal is also used to distinguish it from the video signal .
The processing of audio signals and the conversion between sound and audio signals ( microphone signal ) are the subject of sound engineering and signal processing .
Frequency range
The frequency range of audio signals is often based on the human hearing range and therefore extends from around 20 Hz to 20 kHz. In order to exclude audible influences on the signal near the two limit frequencies, devices and storage media (e.g. Super Audio CD , DVD-Audio ) are used for particularly high demands in hi-fi and studio technology as well as general applications (e.g. animal recordings, ultrasound ) used with a much wider frequency range.
Examples
- Signals from music cassettes: typically 50 Hz to 12 kHz
- Professional audio tape signals: 15 Hz to 18 kHz
- Theoretical bandwidth of the compact disk: 0 Hz to 22.05 kHz
- Theoretical bandwidth of the SACD: 0 Hz to 48 kHz
- Signal from simple stage microphones: 35 Hz to 15 kHz
- Signal from good studio condenser microphones: 5 Hz to 22 kHz
- Usable range of studio measurement microphones 3 Hz to 45 kHz
- Bandwidth of good hi-fi amplifiers: 10 Hz - 30 kHz
- Bandwidth of good studio amplifiers: 5 Hz - 40 kHz
- Bandwidth of ultrasonic microphones: typically 1 kHz - 150 kHz
In the case of digital audio signals, the audio signals are transmitted and processed as numerical values, the sampling rate determining how many such numerical values are recorded and processed per second. Depending on the audio format and number of channels, digital audio signals have e.g. T. bandwidths up to 10 MHz.
Signal strength
The strength of an audio signal is generally referred to as its level . In the case of analog audio signals, the signal level corresponds directly to the amplitude of the electrical voltage , which in turn is proportional to the sound pressure or the speed of sound .
With digital audio signals, the technical signal level is independent of the volume and is determined by the data transmission device.
Types of beeps
According to psychoacoustics , tones of speech and music are in most cases complex tones, i.e. sound signals that can be described as a sum with a finite number of sinusoidal partials . One can make three broad distinctions.
- Harmonious complex tones
- Approximately harmonic complex tones
- Slightly harmonious complex tones
Harmonious complex tones
A distinction between purely harmonic and in-harmonic complex tones is practically impossible or only possible with a certain probability on the basis of physical criteria. In general, harmonically complex tones are called those which are periodic and whose fundamental tone corresponds to the pitch that is mainly perceived. The second criterion can be verified by comparing the pitch of the auditory with sine tones . These complex tones include almost all physically generated tones, voices and speech.
Approximately harmonic complex tones
Tones that are approximately harmonically complex are those whose higher frequency components have a non-integer relation to the fundamental frequency and which already have a non-negligible proportion of inharmonicity .
Slightly harmonious complex tones
Low harmonic complex tones are tone signals whose partial tone frequencies differ considerably from the harmonic pattern. This includes all sounds that are created by striking bells, rods or tubes or membrane-like bodies. Common musical instruments of this type are glockenspiel , xylophone , marimbaphone , kettledrum and drums . The frequencies of the natural vibrations of bells, plates, rods or membranes are not in a harmonious relationship to one another from the outset and must first be brought into an approximately harmonious relationship through targeted processing and shaping.
Individual evidence
- ^ Acoustic communication: Basics with audio examples, Ernst Terhardt, 1998 ISBN 3540634088 , online