Directional Acoustic Measurements Using Shaft Encoder
Original Publication Date: 1985-Jul-01
Included in the Prior Art Database: 2005-Feb-18
In directional three-dimensional acoustic measurements a rotating boom carrying a number of microphones located above a machine under test is coupled to a shaft encoder to accurately encode horizontal angular boom position. This is repeated for each microphone in a ring in the hemisphere over the machine being tested. Data from the shaft encoder and each microphone noise spectrum are processed to provide displays, representing a map of noise generated for each microphone by the machine, giving a hemispherical map enabling noise-generating areas of the machine to be detected. Fig. 1 illustrates the noise map produced by the ring 1 or path followed by a single microphone with four longitudinal lines (North, South, East and West) marked around reference ring 4. Two noise level peaks are shown at 2 and 3. Fig.