On Generating Mechanisms for External Tire Noise

An analysis of available tire noise data seems to indicate that external noise emission from tires on dry roads is mainly caused by radiation of vibrations from the tire-road interactions. Indications of this are:

1. 1.
   Speed dependence of random-tonal-and squeal noise.
2. 2.
   The power spectral density versus speed and frequency (by using a novel data-reducing technique for tire-noise).
3. 3.
   The connection between n and C in the formula
   Where:

   L

   is sound level dB(A),

   C

   is regression constant,

   V

   is vehicle speed, and

   n

   is velocity exponent.

   All tires and road surfaces constitute a straight line.
4. 4.
   External noise dependence on the macro-texture of the road.
5. 5.
   Connection between the normalized PSD versus structure number and PSD versus space frequency of the roughness of the road surface.

The paper points out the possibility of tangential movements of tread elements as a source of high-frequency external noise from tires on dry road surfaces.

For wet roads, the tire noise normalized spectrum in the lower frequency region would suggest some turbulent fluid-dependent mechanism while transients from braking up the water film may be responsible for the noise at higher frequencies.