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Demystifying the Rumbling Noise Generated from the Elevator Machine Room

When an elevator is operating, there is often a cacophonous rumbling sound emanating from its machine room. Commonly the elevator companies claim no responsibility, citing that the overall sound pressure level (SPL) is legally compliant. However, clearly, SPL alone cannot fully represent the perceivable sound quality of the noise from the machine room. A smart phone has been used to record this noise, and the audio clip has been converted into time-domain signals. These digitalized signals have then been comprehensively analyzed by tools such as, but not limited to Fast Fourier Transformation (FFT), Short-time Fourier Transformation (STFT), and Wavelet functions. This visualized noise analysis in turn points to the fact that it is the tonality and fluctuations in the noise signal that make the acoustic noise of elevator machine so jarring to the ears despite its acceptable SPL level, prompting the negative psychoacoustic reactions of the residents. The resulting analysis demystifies the noise and has convinced elevator companies to replace their machines, paving a new path to be used for victims globally suffering from discomforting elevator noise. Furthermore, elevator companies should use similar analysis to improve its designs and manufacturing so as to improve overall perceived sound quality.