Room acoustics and acoustic properties - decibel A, B and C - Noise Rating (NR) curves, sound transmission, sound pressure, sound intensity and sound attenuation
Speed of sound in air at standard atmospheric pressure with temperatures ranging -40 to 1000oC (-40 to 1500oF) - Imperial and SI Units.
Logarithmic unit used to describe ratios of signal levels - like power or intensity - to a reference level.
Sound pressure filters compensating for hearing sensed by the human ear.
The sound generated by a fan depends on the motor power, the volume capacity, the static pressure increase and the discharged volume.
Human activities like walking, running and dancing - and operating machines - can introduce floor vibrations due to resonance.
Speed of sound in some gases at zero degrees Celsius and atmospheric pressure.
Noise attenuation in rectangular straight, lined, sheet metal ducts.
Speed of sound in common fluids like water, glycerol, kerosene and more.
Maximum recommended sound pressure levels in rooms like kindergartens, auditoriums, libraries, cinemas and more.
Noise Criterion - NC - level is a standard describing relative loudness of a space with a range of frequencies
Acceptable noise - dBA - level at typical common locations.
The noise level should not exceed certain values to protect public health and welfare.
Maximum daily noise dose level when exposed to periods with different levels.
The NIOSH noise Recommended Exposure Limit - REL - for occupational noise
Calculate Noise Criterion (NC) from octave band pressure levels.
Comparing Noise Criterion (NC, NCB, RNC) to Noise Rating (NR) and dB(A).
Exposure to noise should be controlled so that it is less than a maximum combination of exposure level and duration.
Barriers and enclosures to reduce noise sound pressure levels from machines.
TheBlade Pass Frequency noise generated by a fan can be very intense and varies with the number of blades and the rotation velocity.
Estimate noise level generated by traffic.
Estimate noise generated by air flow in ducts.
Sound power noise generated by blade dampers in ventilation systems.
An online Noise Rating (NR) calculator.
Frequencies vs. notes and octaves.
The Noise Rating (NR) Curve used to determine acceptable indoor environments for hearing preservation, speech communication and annoyance.
The octave and the 1/3 octave band frequencies.
Outdoor ambient sound pressure levels (dBA) in rural and urban business and industrial environments with or without limited traffic.
A noise measurement system for continuous or ambient noise in indoor environments.
An online Preferred Noise Criterion (PNC) calculator.
The transmission of outdoor sound through and around barriers - the Fresnel Number.
In a room the sound or noise will reach the receiver as direct and reverberant sound.
The propagation of outdoors sound vs. distance and attenuation.
The Room Criteria (RC) is used to measure background noise in buildings for frequencies ranging 16 to 4000 Hz.
Distance and perception of voice.
The logarithmic decibel scale is convenient when adding values for signals like sound power, pressure and more from two or more sources.
Background noise frequencies that interferes with speech.
Speed of sound in solids and metals like aluminum, brass, concrete and more.
The disruption of the sound pressure wave and the reduction of noise is called attenuation - Sound Pressure Level vs. distance calculator.
The speed and attenuation of sound in moist air varies with sound frequency and air humidity.
The attenuation in a room depends on the location of the sound source and the receiver - and the room constant.
The doppler effect is the change in sound frequency due to the relative motion between a source and a listener.
An introduction to the nature of sound with frequencies, wave-lengths and octaves.
Shift in hearing threshold for men and women vs. age.
The EPA A-weighted sound level day and night equivalent definition - Ldn - for a 24 hour period.
The EPA Equivalent Sound Level - Leq - quantifies the noise environment to a single value of sound level for any desired duration.
The EPA Sound Exposure Level - Ls - describes the noise from a variable source.
The sound reverberation time indicates how long it takes until the sound pressure level in a room is decreased with 60 dB.
Mean absorption coefficients and reverberation times in typical rooms.
Room sound absorption and absorption coefficients for common materials like plaster walls, brickwork, plywood panels and more.
Room size, absorption characteristics - and attenuation in direct sound fields.
Estimating sound attenuation where ducts splits to terminals.
Sound attenuation from main ducts to branch ducts.
Noise attenuation in duct elbows by reflected sound.
Low frequency noise transferred from main duct to end terminals is reflected back to main duct.
Acoustic power of sound per unit area.
Introduction to decibel, sound power, intensity and pressure.
Calculate sound level, pressure and intensity.
Sound power from sources like fans, jet engines, cars, humans and more.
Sound Pressure is the force of sound on a surface perpendicular to the propagation of sound.
OSHA maximum A-weighted sound pressure levels allowed per day.
Doubling of the distance from a noise source reduces the sound pressure level with 6 decibel.
Sound transmission from ducts to surrounding rooms.
Sound transmitted through duct walls, floors and ceilings.
Sound transmission and attenuation in building elements like massive concrete walls or floors.
A free online speed of sound calculator.
Calculate the speed of sound (the sonic velocity) in gases, fluids or solids.
Change in sound pressure level and the subjective human perception.
Noise attenuation in unlined sheet-metal ducts.
Satisfactory, difficult and impossible noise levels for telephone use in noisy areas.
Acoustic noise calculation procedure HVAC systems.
Noise in a ventilation system can be reduced by reactive, diffuser type, active and/or dissipative silencers.
Speed of sound in water at temperatures ranging 32 - 212oF (0 - 100oC) - Imperial and SI units.