Sound power level is now an important factor for measuring noise. Since the conventional noise measurement, the sound pressure level (SPL) at 1.0 m points from the measurement object, is easily influenced by the surrounding environment, manufacturer needs to constantly pay attention to the environments where they make the measurement of noise. For example, if the environment where the product is used and the condition in which the manufacturer tests are different, the measured SPL may not be equal. From both users and the manufacture's point of view, "the representative quantity which is not influenced by the environment and which depends on noise source only" is preferred and suitable. Sound power level, which is obtained by integrating total sound energy from the hypothetical measurement surface which surrounds completely the source of the noise, is the suitable quantity for product labeling, as well as being an important parameter of a sound source for noise simulation.
Determination of the sound power levels of a noise source using sound pressure has been standardized to ISO 3740 series, ISO 7795, JIS Z 8732, 8733 and 8734. The measurement which targets the stationary noise source in an anechoic room or semi-anechoic room, using a microphone traverse system makes the positioning of the discrete measurement points easier and enables to reduce the labor cost, compared to a single channel measurement using a single microphone. We can propose a sound power level measurement system using a wide variety of microphone traverse system such as with a circular rail; a ceiling installed 5 axes, the combination of the Cartesian coordinate type traverse and a turntable.
To capture the transit or impulsive phenomena, the traverse systems working with a multi-channel data acquisition system are available.
Furthermore, sometimes, the telescopic multi-microphone traverse with rotating tip is very effective, since it can change the size of the measurement surface according to the size and the shape of the object.
