Page layout

– definitions –
– explanations –
– correlations –

“currently under construction”


Definition “sound pressure level”

The physical magnitude of the sound pressure level indicates the measurable sound pressure level of a hearing event.

Also called: Volume

Symbol: Lp

SI unit: dB spl

Definition “volume”

The psychoacoustic magnitude loudness indicates the subjectively perceived volume of a hearing event.

Also called: volume level

The value depends on the frequency and the sound pressure level.

Symbol: LN

SI unit: phon

Definition „loudness“

The psychological unit loudness defines the subjective perception of sound. If loudness is doubled it means that the percepted volume is doubled.

Symbol: N

SI unit: sone

Formula: 1 sone = 40 phon (@sine 1kHz 40 dB spl)

Hörschwelle: 0 sone

Normallautheit (Unterhaltung): 1-2 sone

Schmerzschwelle: 676 sone

Correlation „N, L­N, Lp

The sound pressure level in dB spl is a physically absolute linear scale of the sound pressure. However, since this is not perceived linearly by human hearing, the sound level is in phon of the relative sound pressure level, adapted to human hearing.


A sound pressure level of 40 dB spl take at 100Hz 10dB quieter than at 1kHz. 40 phon define 40 dB spl at 1kHz and 50dB spl at 100Hz to unify this phenomenon.

The loudness builds up on the volume and sets this relative size, however, relative to the change in volume.


If 40 dB spl is applied at 1 kHz (as 40 phon), this is 1 sone. A change of 6dB spl at 1kHz corresponds to a change in volume to 46 phon and 2 sone.

Definition „tonality“

The psychoacoustic magnitude of tonality defines the perceived pitch of a sinusoidal oscillation.

Symbol: Z

SI unit: mel (melody)

The mel-scale was invented by Stanley Smith Stevens.

The difference to the absolute pitch expressed in frequency f lies in the slight altered perception in the high frequencies.

A physical octave (doubling of the frequency) corresponds to a psychoacoustic interval of more than 2.5 octaves.


Explanation “traveling wave”

Named by Georg von Békésy.
The wave movement, which takes place in the inner ear, is referred to as a traveling wave. The sound pulse is passed from the stirrup to the oval ear (membrane on the inner ear) where it is converted into a wave motion in the fluid in the inner ear. This wave now passes through the anterior canal of the auditory canal and flows through the tympanum through the round window at the end of the auditory canal. Depending on the strength of the wave, the basilar membrane is set in motion. This is initially very thin and stiff and in the end thicker and more flexible. Accordingly, it is initially more sensitive to high frequencies and ultimately more sensitive to low frequencies. The wave, which now runs along the basilar membrane, is called a traveling wave.

Explanation “Haas effect”

Named after Helmut Hass (1951).
The hate effect describes a psychoacoustic phenomenon, which describes the localization of sound events. Only the first wavefront is found, which is physically dependent on the direct sound. Thus, the source can always be located, if it is a hearing event, even if the reflections are louder than the direct sound. The following wave fronts are used to assess the size and composition of the room.


Correlation “continuous sound pulse to loudness”

The loudness is dependent on the duration of the sound pulse. This is the reason why the loudspeaker is not the peak, but the RMS is relevant.