It is a measure of force per unit area i.e. equivalent to the N/m

1

1 μPa = 1 micropascal = 10

SI unit is the pascal-second per metre (Pa·s/m).

**Partial Definition** IEC 801-30-02, sinusoidal component of a complex sound wave

On the other hand an object, like a cricket ball experiences **acceleration, velocity and displacement** literally so the general acceleration, displacement and velocity terms are more apt.

See also • instantaneous particle acceleration

See also • peak particle displacement

**Particle 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)

See also • peak particle velocity

v is the effective

vo is the reference particle velocity = 5 x 10

The following notations : dB SVL, dB(SVL), dBSVL or dBSVL are often seen but are not strictly correct

Pascal (symbol Pa)

Passive Sound Absorber

**pC (picocoulomb)** : 1 pC = 10^{-12} Coulomb

*PE •* piezoelectric

See also time weightings

Peak Frequency-weighted Sound Pressure Level

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.

See also • particle velocity • PPV measurements.

Peak Sound Level

Peak Sound Pressure

Peak Speech Power

Peak-to-Peak Sound

● 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.

See also • effective perceived noise level • judged perceived noise level • maximum perceived noise level • noise exposure forecast • noise and number index • tone-corrected 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.

Permanent Threshold Shift (PTS)

*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.

See also • 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.

● 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.

Plane Wave or Planewave

Some UK planning policy guidance is available for downloading.

*PNC •* preferred noise criterion

*PNL •* perceived noise level

*PNLmax •* maximum perceived noise level

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.Potential Sound Energy Density.

W = J/s joule per second = N m/s newton metre per second : base unit m

See also our full page on sound power and related parameters.

Power Level

**A** root-power quantity is a quantity, like sound pressure, which when squared is proportional to the sound power.

**Power Spectral Density Definition** IEC 801-21-44, limit as the bandwidth approaches zero, of sound power divided by Bandwidth

**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.

**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

*Preferred frequency* is also known as nominal frequency.

Preferred Speech Interference Level (PSIL)

**Presbycusis** impairment of hearing with age.

See also • atmospheric pressure • static pressure • sound pressure and related parameters

Because of their importance in acoustics we have a full page on measurement microphones

See also • free-field microphones • random incidence microphones

Pressure Residual Sound Intensity Index

Privacy Index

Progressive Waves

*Propagation* •
sound propagation •
sound propagation coefficient •
sound transmission

Also known as transmission loss, but should not to be confused with sound insulation transmission loss

*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.

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

*PSIL •* preferred speech interference level

**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

See also • complex sound • tone