Hvorfor er flatt mest nøytralt når alle opplever fallende nærmest virkeligheten?
Hva betyr nøytralt for deg da i så fall?
La meg svare på en litt omstendelig måte. Temaet er såpass sentralt at jeg synes det forsvarer tiden og plassen.
Frederick Alton Everest (1909-2005) skrev boken
Master Handbook of Acoustics, en av de mestselgende bøkene om akustikk. Her skriver han om både målinger og flat kurver, slik (min utheving midt i teksten):
«White and Pink Noise
References to white noise and pink noise are common and sometimes confusing. What is the difference? White noise is analogous to white light in that the energy of both is distributed uniformly throughout the spectrum. In other words, white noise energy exhibits a flat distribu- tion of energy with frequency (Fig. 5-18A). White light sent through a prism is broken down into a range of colors. The red color is associated with the longer wavelengths of light, that is, light in the lower frequency region. Pink noise is noise having higher energy in the low frequencies. In fact, pink noise has come to be identified specifically as noise exhibiting high energy in the low-frequency region with a specific downward slope of 3 dB per octave (Fig. 5-18C). There is a practical reason for this specific slope. These two colorful terms arose because there are two types of spectrum analyzers in common use. One is the constant bandwidth analyzer, which has a passband of fixed width as it is tuned through- out the spectrum. One well-known analyzer of this type has a band- width of 5 Hz. If white noise with its flat spectrum were measured with a constant-bandwidth analyzer, another flat spectrum would result because the fixed bandwidth would measure a constant energy throughout the band shown in Fig. 5-18A.
Another very popular and convenient spectrum analyzer is the constant percentage bandwidth analyzer. In this instrument the band- width changes with frequency. An example of this is the one-third- octave analyzer, commonly used because its bandwidth follows reasonably well with the critical bandwidth of the human ear through- out the audible frequency range. At 100 Hz the bandwidth of the one- third-octave analyzer is only 23 Hz but at 10 kHz the bandwidth is 2,300 Hz. Obviously, it intercepts much greater noise energy in a one- third octave band centered at 10 kHz than one centered at 100 Hz. Measuring white noise with a constant-percentage analyzer would give an upward-sloping result with a slope of 3 dB/octave, as shown in Fig. 5-18B.
In audio-frequency measurements, the desired characteristic of many instruments, rooms, etc. is a flat response throughout the frequency range. Assume that the system to be measured has a characteristic almost flat with frequency. If this system is excited with white noise and measured with the very convenient constant-percentage analyzer, the result would have an upward slope of 3 dB/octave. It would be far more desirable if the measured result would be close to flat so that deviations from flatness would be very apparent. This can be accomplished by using a noise with a downward slope of 3 dB/octave. By passing white noise through a filter, such as that of Fig. 5-19, such a downward sloping exci- tation noise can be obtained. Such a noise, sloping downward at 3 dB/octave, is called pink noise. A close-to-flat system (amplifier, room) excited with this pink noise would yield a close-to-flat response, which would make deviations from flatness very obvious. For such reasons pink noise is here to stay».
Her bruker Everest ordet flat som en ønsket karakteristikk fra instrumenter til rom, at det er praktisk med flate kurver (avvik blir mer åpenbare), og han kaster lys (sic!) over bruken av ordet «farge» innenfor lyd.
Everest bruker ikke begrepet «nøytral» selv, men han bruker ofte uttrykket «farget» og «fargelegging», bl.a. slik: «
Unquestionably, sound in such a cubical space would be highly colored and acoustically very poor» og «
colorations largely determine the quality of sound for a small studio or listening room».
Til sammenlikning bruker den tidligere nevnte
Philip Newell uttrykkene «nøytral» og «nøytralitet»
Recording Studio Design (4. utg. fra 2017), f.eks. slik:
«If the room is of an idiosyncratic nature, the required neutrality is unlikely to be achieved».
Olson skrev for 70 år siden følgende:
«Comments from both music critics and layman were that tone color, dynamic range, and general fidelity of the reproduced sound matched the over-all response frequency characteristic of the recording and orchestra so closely as to be practically indistinguishable from the original sound».
Poenget mitt er at »nøytralt» og avvik fra nøytralt - «farget» - brukes i bøker og artikler om lyd og akustikk, både i dag og for mange tiår siden. Spørsmålet om hva «nøytralt» betyr, burde derfor reises til kjente fagpersoner som Olson, Everest, Newell m.fl. «Nøytralt» og «farget» er ord som dukker opp så ofte i fagdiskusjoner om lyd at jeg tror slike tekster blir enklere å forstå hvis man selv legger en innsats i å forstå hva disse ordene betyr.
Legg for øvrig merke til at både «nøytralt» og spesielt «farget» er metaforer som brukes for å kommunisere mer spesifikke tekniske begreper. Noen ganger er metaforer gode, andre ganger bommer de. Jeg mener at disse metaforene - nøytral og farget - er gode. Og disse metaforene er - som Everest viser med sitt fargeeksempel - helt løsrevet fra smak og preferanser.
Svarte jeg på spørsmålet ditt? Jeg tror Olson, Neweell, Everest m.fl. ville sagt at det er nøytralt når en anekoisk flat høyttaler avspilles flatt i rommet med «rosa støy» (vel vitende om at andre ting enn frakvensrespons dekkes av nøytralitetsbegrepet). Enig?