Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrophone. The SI unit of sound pressure is the pascal (Pa).
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👉 Sound pressure level in the context of Bass amplifier
A bass amplifier (also abbreviated to bass amp) is a musical instrument electronic device that uses electrical power to make lower-pitched instruments such as the bass guitar or double bass loud enough to be heard by the performers and audience. Bass amps typically consist of a preamplifier, tone controls, a power amplifier and one or more loudspeakers ("drivers") in a cabinet.
While bass amps share many features with the guitar amplifiers used for electric guitar, they are distinct from other types of amplification systems, due to the particular challenges associated with low-frequency sound reproduction. This distinction affects the design of the loudspeakers, the size and design of the speaker cabinet and the design of the preamplifier and amplifier. Speaker cabinets for bass amps usually incorporate larger loudspeakers (e.g., 15 inches (380 mm) speakers are more common for bass than for electric guitar amps) or more speakers and larger cabinet sizes than those used for the amplification of other instruments. The loudspeakers themselves must also be sturdier to handle the higher power levels and they must be capable of reproducing very low pitches at high sound pressure levels.
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Sound pressure level in the context of Equal-loudness contour
An equal-loudness contour is a measure of sound pressure level, over the frequency spectrum, for which a listener perceives a constant loudness when presented with pure steady tones. The unit of measurement for loudness levels is the phon and is arrived at by reference to equal-loudness contours. By definition, two sine waves of differing frequencies are said to have equal-loudness level measured in phons if they are perceived as equally loud by the average young person without significant hearing impairment.
The Fletcher–Munson curves are one of many sets of equal-loudness contours for the human ear, determined experimentally by Harvey Fletcher and Wilden A. Munson, and reported in a 1933 paper entitled "Loudness, its definition, measurement and calculation" in the Journal of the Acoustical Society of America. Fletcher–Munson curves have been superseded and incorporated into newer standards. The definitive curves are those defined in ISO 226 from the International Organization for Standardization, which are based on a review of modern determinations made in various countries.
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