Spectral difference
The word spectral difference belongs to acoustics and to human directional hearing .
With the help of the signals perceived by both ears , it is possible to recognize from which direction and from which distance a sound event is arriving. The auditory impression is evaluated according to the transit time difference , level difference (volume difference ) and spectral difference .
Some sound professionals believe that stereo recordings for loudspeakers ( loudspeaker stereophony ) can be improved by using microphone systems with two microphones that generate head-like signals with frequency-dependent level differences (spectral differences) through separators . What is forgotten is that the wrong timbre differences from both loudspeakers in the stereo triangle are radiated "unnaturally" to both ears (4 ways) and that the ears of the listener through the auricles and bending around the head only form their own correct spectral differences themselves than special human frequency-dependent level differences.
The level difference or the level difference of the sound pressure at the ears is strongly frequency-dependent (spectral difference) and shows great differences from person to person. Just as there are only one-time fingerprints, the word ear prints is also used in English to show the human differences in hearing.
The artificially generated frequency-dependent level difference (spectral difference) disturbs the sense of direction and the comb filter effects resulting from the superimposition of the timbre differences (timbre differences) are audible.
Ear signals : When hearing a sound source naturally from the 30 ° direction, there is an interaural frequency-dependent level difference of ILD = 4.2 to 6 dB (spectral difference) or an interaural transit time difference of ITD = 0.25 to 0.31 ms.
What is meant by spectral difference? Microphone systems with separators of any kind, including artificial heads with or without auricles or microphones that do not show parallel in AB stereophony, create spectral differences between the two channels as a system, that is, frequency-dependent level differences that increase with frequency. These spectral differences are produced by your own head with its ear system during natural hearing. The assumption that spectral differences are therefore also required for loudspeaker stereophony is not correct. Spectral differences in the stereo loudspeaker signals lead to discoloration of the sound.
With stereo listening in a stereo triangle , the locations of the phantom sound sources on the loudspeaker base are localized and indicated by the direction of the hearing event as a deflection in percent from the center. Frequency-neutral level differences and time-of- flight differences lead to shiftable phantom sound sources through cumulative localization . With loudspeaker stereophony , frequency-dependent level differences are to be avoided; these are spectral differences because these lead to sound discolouration in the case of lateral sound incidence .
It is not possible to make a precise statement about when spectral differences can be heard as sound discoloration. The tolerance limits are quite different from person to person. Whether a sound coloring is tolerable, harmful or even a desired effect is up to the listener.