-
A-Weighting
The A-weighting curve is widely adopted for environmental noise measurement -
Sound Power
A sound source radiates power and this results in a sound pressure -
Noise Outside
Sound waves travel in a continuously expanding spherical wavefront from the source -
Adding Noise
When adding two sound sources together the total sound level does not double -
Sound Transmission
The Source of a noise is what is creating a noise nuisance.
A-Weighting
The A-weighting curve is widely adopted for environmental noise measurement and is standard in most sound level meters. This curve shows that sounds at 50 Hz would have to be amplified by 30 dB to be perceived as equally as loud as a sound at 1000 Hz at normal sound levels.
Sound Power
A sound source radiates power and this results in sound pressure. Sound power is the cause. Sound pressure is the effect. The relationship between sound power and sound pressure is very similar. What we hear is sound pressure, but it is caused by the sound power emitted from the original source.
Noise Outside
Outdoors, sound waves travel in a continuously expanding spherical wavefront from the source. For a point source that emits a certain sound energy, this energy is concentrated in a single point at the source. At a distance from the source, the same energy is distributed over a sphere. The greater the distance from the source, the larger the surface over which the energy ends up being dispersed.
Adding Noise
When adding two sound sources together the total sound level does not double, this is because decibels are expressed in logarithmic values so simple addition and subtraction cannot be used. Perceived loudness is typically a subjective term describing the strength of the ear’s perception of a sound. A widely used ‘rule of thumb’ for the loudness of a particular sound is that the sound must be increased in intensity by a factor of ten for the sound to be perceived as twice as loud.
Sound Transmission
Ideally, this is the area that should be considered for treatment first when trying to control a noise problem. The Transmission path is the most variable of the three areas, as noise can travel through air or through structural vibration. Vibration is transmitted structurally through a building causing walls in other areas to vibrate and radiate noise. Treatment of the transmission path reduces the noise reaching the receiver. While the Receiver of noise may be a person or room or even a whole community in the case of aircraft noise. In some cases treating the receiver may be the only noise control option, but it is by far the most complex & expensive.
