### Explanation “longitudinal wave”

A wave propagation in a two-dimensional plane is called the longitudinal wave.
One molecule encounters the other.
The particles of the carrier medium oscillate parallel to the propagation direction.

### Explanation “transverse wave”

A wave propagation in the classical “wave form” is called a transversal wave.
The particles of the carrier medium vibrate orthogonally to the propagation direction.

### Explanation “natural frequency”

The natural frequency is the frequency of a vibrating system that has been triggered by a single impulse.

### Explanation “elongation”

Elongation is the oscillation deflection at a certain point in time.

### Explanation “distance law”

With regard to the spherical emission of sound and its sound pressure level in the direct sound field
When the distance is doubled, the sound pressure level decreases by 6dB.

### Explanation “frequency superposition”

If two phase-equal frequencies are superimposed, doubling occurs.

### Explanation “frequency cancellation”

If two frequencies phase shifted by 180 ° are superimposed, there is an extinction.

### Explanation “frequency hovering”

A hovering is caused by the superposition of two similar frequencies.

For exampe: C3 & C3 + 25cents

### Explanation “Doppler effect / sound compression”

Why is it that a sound event appears to the listener higher when it moves toward it?
At the compression of the sound waves.
Based on the Doppler effect, the distance of the longitudinal waves is shortened by the upward movement as these are generated by the signal source.

### Explanation “comb filter effect”

When two oscillations of different wavelengths are superimposed, periodic cancellations occur in the frequency response.

### Explanation “Huygens principle”

The Huygen principle states that every point of a wavefront can be seen as the new starting point of a new wave (elementary wave).
The wave diffraction and wave breaking is explained by the Huygen principle.

### Explanation “Reverberation time RT60”

The reverberation time RT60 specifies how long the sound needs after the signal source has been interrupted to drop 60dB in the level.

### Explanation “Overtones and harmonics”

Overtones or harmonics are integer multiples of the fundamental frequency with decreasing amplitude.

1. harmonic = base frequency
2. harmonic = 1. overtone (lower amplitude)
3. harmonic = 2. overtone (lower amplitude)

### Explanation “White noise”

A white noise includes all frequencies at the same power. On a logarithmic frequency scale, this forms a straight line parallel to the X axis, since low frequencies have more energy than high, high frequencies, but represent a wider frequency spectrum.

### Explanation “Pink noise”

A pink noise includes all frequencies with the same energy per octave. Since an octave at low frequencies covers a lower frequency spectrum than at high frequencies, this results in a proportionally falling line at a logarithmic frequency scale.
Since the human ear is more sensitive at high frequencies, the pink noise is more linear than the white noise.
Each octave has a level drop of 3dB spl.

### Explanation “Red noise”

A red noise, or brown noise (after Robert Brown), is similar to the pink noise, but drops by 6dB spl per octave. This corresponds to a drop of 20dB spl per decade.

### Explanation “Grey noise”

The grey noise includes all frequencies with the same loudness, following the psychoacoustical sound curve.

### Explanation “Correlation: Diaphragm size (source) to wavelength (sound)”

If the diaphragm size of the signal source is higher than the wavelength of the sound event, the radiation response is more directed. If the membrane size is less than the wavelength of the sound event, the radiation response is rather spherical.