Editorial Type:
Article Category: Research Article
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Online Publication Date: 01 Jan 2018

Experimental Investigation of Tire Slap Noise

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Page Range: 38 – 52
DOI: 10.2346/tire.18.460101
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ABSTRACT

Tire noise is an important issue both in the vehicle interior and to the vehicle exterior, since it affects passenger comfort and environmental noise levels, respectively. Such noise is increased when a tire encounters discontinuities on the road surface, the discontinuity being either a gap or a bump. The relatively high frequency (e.g., approximately 1 kHz and above) airborne tire noise generated by such discontinuities is defined as tire slap noise in this study.

Most previous research on noise generated by surface discontinuities has been focused on lower frequency tire noise, typically below 600 Hz, and, in particular, on structural-borne noise transmitted from the tire into the vehicle associated with the acoustic modes of the tire interior. Here, instead, the focus is on higher frequency airborne transmission. Further, the study here is conducted from the perspective of tire structural vibration, which concerns the vibration of and sound radiation from the tire treadband structure, rather than tire pattern noise, for example.

The high frequency tire slap noise was investigated in a laboratory environment. The measurements were conducted by using the Ray W. Herrick Laboratories' Tire Pavement Test Apparatus (TPTA), on which a loaded tire can be run on realistic road surfaces at speeds up to 50 km/h; the resulting tire noise was measured using the On-Board Sound Intensity (OBSI) method. A gap between two different concrete surfaces was chosen as the road discontinuity, and both narrow band and one-third-octave band spectra were recorded over the gap and over the adjacent smooth road surface segments.

Several tires were tested on the TPTA, and their slap noise was recorded. Surface noise and slap noise were compared up to 1600 Hz to show the impact of the discontinuity on the tire noise radiation. Generally, slap noise is of a higher level than the surface noise, especially between 800 and 1400 Hz, but some tires showed distinct differences between the noise response on the surface and over the gap, while other tires radiated similar noise on both the surface and over the gap. Moreover, static tire mobility measurements were performed to investigate the wave type responsible for the different responses on the gap and the surface.

Keywords: slap noise; sound radiation; tire; vibration; surface discontinuities
FIG. 1
FIG. 1

Set up of the TPTA in the Herrick Laboratories semi-anechoic chamber.

FIG. 2
FIG. 2

(a) Phase-matched microphones, (b) tri-axial accelerometers.

FIG. 3
FIG. 3

(a) Selected gap, (b) selected pavement surface.

FIG. 4
FIG. 4

(a) Magnetic trigger installation, (b) trigger location for slap noise.

FIG. 5
FIG. 5

Tire B (a) sound pressure level spectrogram, (b) segmented time history of gap noise.

FIG. 6
FIG. 6

(a) Sound pressure level, (b) x-direction wheel center acceleration, (c) y-direction wheel center acceleration, (d) z-direction wheel center acceleration.

FIG. 7
FIG. 7

Sound pressure level on gap and surface for (a)Tire A, (b)Tire C, (c)Tire D, (d)Tire E.

FIG. 8
FIG. 8

Sound pressure level difference in 1/12 octave band for gap and surface.

FIG. 9
FIG. 9

Illustration of tire surface velocity measurement.

FIG. 10
FIG. 10

Tire E circumference (a) absolute mobility, (b) dispersion relation, (c) dispersion relation zoomed in the 800–1800 Hz range.

FIG. 11
FIG. 11

Tire E cross-section 5° to drive point (a) real mobility, (b) cross-section average mobility. Vertical dashed lines indicate approximate location of the shoulder. (c) Cross-section average mobility multiplied by the circumferential zero wavenumber component

Contributor Notes

1 Corresponding author. Ray W. Herrick Laboratories, School of Mechanical Engineering, Purdue University, 177 South Russell Street, West Lafayette, Indiana 47907-2099, USA. Email: cao101@purdue.edu
2 Ray W. Herrick Laboratories, School of Mechanical Engineering, Purdue University, 177 South Russell Street, West Lafayette, Indiana 47907-2099, USA. Email: bolton@purdue.edu
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