Numerical results indicate that the vibrating steel bridge radiates high-level noise because of its extreme flexibility and large surface area for sound radiation.
In Japan, Ban and Miyamoto [10] conducted a study on the noise reduction effects of ballast layers on concrete bridges; the results showed that the noise radiated underneath the bridge could be reduced by 7 dB(A).
Xie et al. [36, 37] proposed a method for calculating the low-frequency noise radiated by bridge vibrations using a highway vehicle bridge coupled vibration model and the principle of the Rayleigh integral method.
By using measured results of the bridge oscillation due to the passage of a vehicle, the infrasound radiated from the bridge is estimated analytically.
The space distribution, spectral characteristics, and SPL of noise radiated by bridges were briefly analyzed.
Finally, the total sound power radiated by the bridge was calculated using the radiation efficiency of each component.
Even though it is difficult to use analytical methods to calculate the sound field radiated by a bridge structure, because it is a complex, elastic body noise source, some researchers have analyzed the sound field radiated by the vibration of box-shaped structures.
This paper addresses this issue, and reports two case studies to quantify the contributions to the total noise level from the wheel/rail noise, and from the noise radiated by the bridge structure itself including both the deck and the parapets.
Low-frequency noise radiated from highway bridges is a serious environmental problem in Japan.
Because the concept of radiation modes can reveal the mechanics of radiation/vibration, it is appropriate to the problem of low-frequency noise radiated from highway bridges.
Then, it is evident that for guitars, designs of fan bracing and bridge are crucial, mainly, in treble sounds radiated by the instruments.
