The phonetic alphabet used in international aircraft communications. The Noise Rating (NR) Curve used to determine acceptable indoor environments for hearing preservation, speech communication and annoyance. Sound power noise generated by blade dampers in ventilation systems. Noise Exposure - Permissible Levels and DurationĮxposure to noise should be controlled so that it is less than a maximum combination of exposure level and duration. Noise Criterion - NC - level is a standard uesd to describe the relative loudness of a space within a range of frequencies.Īcceptable noise - dB A - level at typical common locations. Maximum recommended sound pressure levels in rooms like kindergartens, auditoriums, libraries, cinemas and more. Sound pressure filters that compensates for the hearing sensed by the human ear. Logarithmic unit used to describe ratios of signal levels - like power or intensity - to a reference level. Human physiology, air quality and comfort temperatures, activity and metabolic rates, health effects of carbon monoxide and more. Noise is usually defined as unwanted sound - noise, noise generation, silencers and attenuation in HVAC systems. 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.

Decibel reference scale