Loading effect on tire noise radiation

Noise radiated by tires is a prominent noise pollution source and it is affected by many different parameters. Here, the effect of static load on the tire noise radiation in a laboratory environment was investigated. The measurement was conducted by using the Tire Pavement Testing Apparatus (TPTA), on which a loaded tire can be run at speeds up to 50 km/hr; the tire noise was measured using the On-Board Sound Intensity (OBSI) method. The tire loading was varied from 500 to 900 pounds, and several different concrete pavements were used, and both narrow band and 1/3 octave band spectra were recorded. It was found generally that increased loading caused an increase in radiated noise below 1 kHz, but at the same time to decrease levels in the 1 kHz to 1.6 kHz rage. To identify whether the latter effect was the result of an acoustical resonance, both a normal tire and a fibrous material filled tire were measured and compared: the fibrous material had essentially no effect, and so it was concluded that the effect related to structural wave propagation in the tire. Moreover, static tire mobility measurements were performed to identify the wave type responsible for this effect.