問題詳情

A new technique known as beamforming has been used for determining noise location of passing vehicles. Traditional pass-by noise tests are useful for detecting the sound level of noise sources on a vehicle during operation. 35 Pass-by noise source identification takes this one step further by identifying the source of the noise as well, so engineers can fine-tune vehicle design to minimize noise.36 NAH operates in a sound’s so-called “near field,” within one or two wavelengths of the source, where sound waves act as circular waves emanating from the source. Beamforming, on the other hand, is more suited to the far field, located at roughly seven wavelengths from the noise source, where sound waves act as planar waves. If you can think of a sound source like a pebble falling in water, then sound emanating from the source is like the waves that come from where the pebble hit. 37 If you are standing far away on the shore, however, the waves no longer look like circles but just a straight line coming toward you. Sound waves behave in the same way. Because measurement sensors can often not be close enough to passing vehicles to be in the near field and perform NAH, beamforming is the preferred technique for noise location in such applications.38 This application note strives to offer best techniques for performing beamforming on passing objects so that the end result is an accurate analysis of noise on vehicles.
(A) When you are close to where the pebble fell, the waves are clearly in a circle, centered on where the pebble fell.
(B) These are measured to ensure compliance with laws that govern acceptable sound emitted from a vehicle.
(C) Engineers can use several analysis techniques to identify noise sources including near-field acoustic holography (NAH) and beamforming.
(D) Beamforming presents several challenges including simultaneously measuring a large number of microphone sensors, transmitting and saving this large amount of acquired waveform data, and being able to quickly process large data sets.
35.

參考答案

答案：B
難度：適中0.583333
統計：A(0),B(7),C(2),D(3),E(0)

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