Pressure gradient and Phase - Amplitude sound field quantity pound pressure gradient receiver pressure omni-directional figure-of-eight - sengpielaudio
 
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● The pressure gradient and the phase
 
Fact: The pressure gradient is ahead of the sound pressure at 90°.
 
Phase of the S signal at the microphone with figure-eight pattern in
opposite to the M signal at the microphone with omni-directional pattern?

See: "Soundfield Quantities of a Plane Wave The Amplitudes":
http://www.sengpielaudio.com/SoundfieldQuantitiesPlaneWaveAmplitude.pdf
 
When looking at the curves of displacement, sound pressure, sound velocity and pressure gradient there comes a question:
 
If the pressure gradient is always 90° ahead to the sound pressure, why is MS stereophony with an omni-directional pressure microphone and a pressure gradient figure-of-eight microphone no problem?
 
Answer:
The frequency response of the pressure gradient increases with frequency at 6 dB/octave. To compensate for this, these microphones are "tuned damped". In the electrical analogy,this represents an RC pad above its transition frequency causes a drop of 6 dB/octave, and shifts the phase constant at −90°. In the whole area in which the "pressure gradient figure-of-eight microphone" has a constant frequency response, thus, the phase is equal to the "pressure omni-directional microphone".

Druckgradient und Druck sengpielaudio

"Schallschnelle und Druckgradient sind nicht das Gleiche": http://www.sengpielaudio.com/SchallschnelleIstNichtDruckgradient.pdf
 
"Mechanische Abstimmung von Mikrofonen 1 - Schall-Druckempfänger http://www.sengpielaudio.com/MechanischeAbstimmungSchalldruck.pdf
 
"Mechanische Abstimmung von Mikrofonen 2 - Schall-Druckgradientenempfänger http://www.sengpielaudio.com/MechanischeAbstimmungDruckgradient.pdf
 
"Membranabstimmung des Mikrofons (Mikrofonabstimmung) - Wikipedia" http://de.wikipedia.org/wiki/Mikrofonabstimmung
 
"State of the membrane resonance in dynamic microphones and condenser microphones"
http://www.ak.tu-berlin.de/fileadmin/a0135/Unterrichtsmaterial/Skripte/Bore_Peus_Mikrofone.pdf#search=Tiefabstimmung
 
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