To measure the sound intensity, it is necessary to use at least two identical microphones that are placed close together in a support structure. The human threshold of pain is approximately 1 W/m². The faintest sounds that the human ear can detect at 1 kHz (in other words, the human hearing threshold) have an intensity of approximately 1♱0⁻¹² W/m². It is measured in units of power per square meter and the SI unit for sound intensity is the watt per square meter (W/m²). In other words, the sound intensity is the rate at which sound energy passes through that unit area.
Noise - Acceptable dB A Level - Acceptable noise - dB A - level at typical common locations.NC - the Noise Criterion - Noise Criterion - NC - level is a standard uesd to describe the relative loudness of a space within a range of frequencies.Maximum Sound Pressure Levels in Rooms - Maximum recommended sound pressure levels in rooms like kindergartens, auditoriums, libraries, cinemas and more.Decibel A, B and C - Sound pressure filters that compensates for the hearing sensed by the human ear.Decibel - Logarithmic unit used to describe ratios of signal levels - like power or intensity - to a reference level.Noise and Attenuation - Noise is usually defined as unwanted sound - noise, noise generation, silencers and attenuation in HVAC systems.Physiology - Human physiology, air quality and comfort temperatures, activity and metabolic rates, health effects of carbon monoxide and more.Acoustics - Room acoustics and acoustic properties, decibel A, B and C, Noise Rating (NR) curves, sound transmission, sound pressure, sound intensity and sound attenuation.If the pressure is doubled the sound pressure level is increased with 6 dB (20 log (2)).P ref = 2 10 -5 - reference sound pressure (Pa) The Sound Pressure Level in decibel can be expressed as The SI-unit for the Sound Pressure is N/m 2 or Pa. The sound pressure is the force (N) of a sound on a surface area (m 2) perpendicular to the direction of the sound.
I ref = 10 -12 - reference sound intensity (W/m 2) Sound Pressure Level The Sound Intensity Level can be expressed as: The SI-unit for Sound Intensity is W/m 2. Sound intensity is the ratio acoustic or sound power to area. The loudest sound power generally possible to encounter is that of a jet aircraft with a sound power of 10 5 W - 170 dB.The lowest sound power persons with excellent hearing can discern is about 10 -12 W - defined as 0 dB in the decibel scale.Sound power can more practically be expressed in a logarithmic scale named Sound Power Level as the ratio of sound power to the sound power at the threshold of hearing - 10 -12 W : Sound power is the energy rate - the energy of sound per unit of time (J/s, W in SI-units) from a sound source. Decibel is a logarithmic unit used to describe ratios of physical values like - like power, sound pressure, voltage, intensity and more.