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A rumble is a continuous deep, resonant sound, such as the sound made by heavy vehicles or thunder. In the context of audio reproduction rumble refers to a low frequency sound from the bearings inside a turntable. This is most noticeable in low quality turntables with ball bearings. Higher quality turntables use slide bearings, minimizing rumble. Some phono pre-amplifiers implement a rumble filter, in an attempt to remove the noise. A heavier platter can also help dampen this. Rumble measurement is carried out on turntables (for vinyl recordings) which tend to generate very low frequency noise originating from the centre bearing and from drive pulleys or belts, as well as from irregularities in the record disc itself. It can be heard as low-frequency noise and becomes a serious problem when playing records on audio systems with a good low-frequency response. Even when not audible, rumble can cause intermodulation, modulating of the amplitude of other frequencies. The ‘unweighted’ response curve is intended for use in assessing the level of inaudible rumble with such intermodulation in mind. ==Turntable design== One way to reduce rumble is to make the turntable very heavy, so that it acts as mechanical damper or low-pass filter, but even with the best turntables a lot of rumble tends to be generated by warped records or pressing irregularities sometimes visible as ‘bobbles’ in the surface. An important factor affecting rumble is low-frequency resonance resulting from pickup arm mass bouncing against stylus compliance. This resonance is usually in the 10–30 Hz region, and will increase rumble as well as reducing tracking ability if not well-damped. Some pickup arms incorporate viscous damping aimed at eliminating such resonance. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Rumble (noise)」の詳細全文を読む スポンサード リンク
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