Particle Acceleration, to accelerate an air particle is to change its velocity over a period of time, the units are m/sec2, where acceleration is the rate of change of velocity per unit time, and is a vector quantity. Also known as sound particle acceleration
See also • instantaneous particle acceleration
Particle Displacement, is the movement of the medium, about it's equilibrium as it transmits an acoustic wave. In most cases this is a longitudinal sound wave, but it can also be a transverse vibration wave. Also known as sound particle displacementpeak particle displacement
Particle Velocity the particles of a medium are displaced from their random motion in the presence of a sound wave. The velocity of a particle during this displacement is called the particle velocity, units m/s. Also known as sound particle velocityParticle Velocity (v) is the speed of a particle and should not to be confused with the speed of sound (c).
Particle Velocity Relationships :
Particle velocity × sound pressure = sound intensity.
Particle velocity = sound pressure ÷ acoustic impedance
Particle velocity = sound intensity ÷ sound pressure
Particle velocity = √(sound intensity ÷ acoustic impedance)
Particle Velocity Level (Lv) is also known as acoustic velocity level and sound velocity level
See also • sound pressure
pC (picocoulomb) : 1 pC = 10-12 Coulomb
PE • piezoelectric
See also time weightings
See also • particle displacement
If measurements are made in 3-axis then the resultant PPV (peak particle velocity) is the vector sum i.e. the square root of the summed squares of the maximum velocities, regardless of when in the time history those occur.
Perceived Noise Level Definition IEC 801-29-11, the frequency-weighted sound pressure level in decibels, obtained by a stated procedure that combines the sound pressure levels in the 24 one-third octave bands centred on 50 Hz to 10 kHz
● Note 1 : the procedure is stated in ISO 3891-1978: Procedures for describing aircraft noise on the ground.
● Note 2 : Perceived noise level is intended to approximate judged perceived noise level.
Percentile noise levels may also include other descriptors i.e. A, C, L or Z weightings. Most common Ln values are A-weighted L10 and L90 levels.
Phase Coefficient under acoustic phase coefficient
This is the basis for the measurement of loudness in phons. If a given sound is perceived to be as loud as a 40 dB sound at 1000 Hz, then it is said to have a loudness of 40 phons.sones
PI Index under sound intensity pressure index
PI • privacy index
Picket Fence Effect information between samples in FFT spectrum analysis may be missing. hanning windows may help
pico (p) a SI prefix = 10-12 • see other SI units
Picocoulomb (pC) : 1 pC = 10-12 coulomb
Picofarad (pF) : a million millionth of a farad, 10-12 farad
Picowatt (pW) : a million millionth of a watt; 10-12
The piezoelectric property of materials is used in transducers that convert acceleration (or force) into electrical signals, and vice versa.
This is useful when using sound analysers with constant percentage bandwidth octave or third-octave filters, the net result is a flat spectrum
Other noise descriptors • ambient noise • background noise • broadband noise • gaussian noise • narrowband noise • periodic • pseudo random noise • random noise • residual noise • specific noise • white noise • wideband noise
They are single frequency devices, usually 250 Hz and include a calibrated barometer to correct for local changes in atmospheric pressure.
Pistonphone Definition IEC 801-28-11, apparatus having a rigid piston which can be given a reciprocating motion of known frequency and amplitude so permitting the establishment of a known sound pressure in a closed cavity of small dimensions
Pitch Definition IEC 801-29-01 that attribute of auditory sensation in terms of which sounds may be ordered on a scale extending from low to high
● Note 1 : the pitch of a complex wave depends primarily upon the frequency content of the stimulus, but it also depends upon the sound pressure and the waveform.
● Note 2 : the pitch of a sound may be described by the frequency of that pure tone having a specified sound pressure level that is judged by subjects to produce the same pitch.
Planning and Noise the Planning Policy Guidance PPG24 sets out the UK Government's policies on different aspects of planning. Local authorities must take their content into account in preparing their development plans.Some UK planning policy guidance is available for downloading.
Point Sound Source Definition IEC 801-29-10, source that radiates sound as if from a single point.We know from the inverse square law that the sound energy level decreases by 6 dB every time the distance between the measurement point and the source is doubled.
See also • line source
Polar Pattern or Polar Response, microphones respond to sound coming from different directions with varying degrees of sensitivity. A plot or graph of this response is called a polar pattern (sometimes polar response curve). Similarly loudspeakers and other sound sources have Polar Responses.
Polar Patterns are frequency dependent, the low frequency response may be almost omnidirectional but the polar pattern will be come more directional as the frequency rises up the audio range.
See also our full page on sound power and related parameters.
Power Spectrum Averaging also called rms averaging, calculates the weighted average of the sum of the squared levels. The weighting is either linear or exponential. Power Spectrum Averaging reduces random fluctuations in the levels but does not reduce the noise floor.See also other types of averaging
Power Spectrum Density Definition under power spectral density definition
Power Spectrum Level the level of the power in a band one hertz wide referred to a given reference power.
PPV • peak particle velocity
Predicted Noise Level Reduction (PNR) is the calculated noise level reduction at the ear when using ear protectors, based on the manufacturers' HML figures and the measured noise levels at the operators position.
Preferred frequency is also known as nominal frequency.
|Frequency||Octave||1/3 octave||Frequency||Octave||1/3 octave||Frequency||Octave||1/3 octave|
|20 Hz||x||200 Hz||x||2000 Hz||x||x|
|25 Hz||x||250 Hz||x||x||2500 Hz||x|
|3.15 Hz||x||x||315 Hz||x||3150 Hz||x|
|40 Hz||x||400 Hz||x||4000 Hz||x||x|
|50 Hz||x||500 Hz||x||x||5000 Hz||x|
|63 Hz||x||x||630 Hz||x||6300 Hz||x|
|80 Hz||x||800 Hz||x||8000 Hz||x||x|
|100 Hz||x||1000 Hz||x||x||10000 Hz||x|
|125 Hz||x||x||1250 Hz||x||12500 Hz||x|
|160 Hz||x||1600 Hz||x||16000 Hz||x||x|
Preferred Noise Criterion (PNC) a noise measurement system for continuous or ambient noise in indoor environments proposed by Leo Beranek in 1971.
Presbycusis impairment of hearing with age.
Because of their importance in acoustics we have a full page on measurement microphones
Direct Proportion, as one value increases, another value increases at the same rate.
Inverse Proportionality, when one value decreases at the same rate that the other value increases.See also • inverse distance law • inverse square law
Other noise descriptors • ambient noise • background noise • broadband noise • gaussian noise • narrowband noise • periodic • pink noise • random noise • residual noise • specific noise • white noise • wideband noise
Pulse Code Modulation and Adaptive Delta Pulse Code Modulation are subclasses of the WAV : waveform audio file format
Pulse Code Modulation, works by taking discrete samples at even intervals (called the sampling rate). Common intervals are 11 kHz, 22 kHz, and 44 kHz. The higher the sampling rate, the better the representation of the original analogue wave and the better the sound quality.
Adaptive Delta Pulse Code Modulation (ADPCM), is a form of compression, is a more efficient way of storing waveforms than 16-bit or 8-bit PCM
Pure Tone, a tone with a single frequency, no harmonics, for example a sine wave.