11. At ordinary sound pressure levels, most humans can hear down to about 20 Hz. 12. In acoustics, loudness is the subjective perception of sound pressure . 13. The treatment of sound pressure level is inconsistent with standard reference works across Wikipedia. 14. Root-mean-square sound pressure being obtained with a standard frequency weighting and standard time weighting. 15. Sound pressure is measured using a microphone and particle velocity using a particle velocity probe16. This allows independent control of the sound pressure levels for the audience and the performers. 17. And as interference decreases, so does the phase difference between sound pressure and particle velocity. 18. Decibels _ named after Alexander Graham Bell _ are the universal measure of sound pressure . 19. The sound field can be described using physical quantities like sound pressure and particle velocity. 20. There are 15 SP ( Sound Pressure ) classes and 5 Park & Pound classes.
