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.
【題組】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)
用户評論
【必勝客】評論
波束成形 （Beamforming）又叫波束成型 、 空域濾波 ，是一種使用傳感器陣列定向發送和接收信號的信號處理技術。 [1]波束賦形技術通過調整相位陣列的基本單元的參數，使得某些角度的信號獲得相長干涉，而另一些角度的信號獲得相消干涉。 波束賦形既可以用於信號發射端，又可以用於信號接收端。