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Acoustic Resonator Arrangement

IP.com Disclosure Number: IPCOM000038885D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Clark, MG: AUTHOR [+2]

Abstract

An air resonator arrangement is provided for reducing low frequency noise, pure tones and, also, for eliminating acoustic beats of two air-moving devices operating together to cool an enclosure for an impact printer. (Image Omitted) As shown in the schematic of Fig. 1, blower unit 10 is used for vacuum removal of ribbon debris from the face of a type band of printer mechanism. The blower unit 11 is used to draw cooling air through the carriage motors which advance print form paper. Both blower units are 3-stage vacuum/compressor blowers that exhaust filtered air through muffler unit 12. The blowers generate considerable noise at the exhaust ports. The noise emission is primarily of low frequency, ranging from 125 to 1000 Hz.

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Acoustic Resonator Arrangement

An air resonator arrangement is provided for reducing low frequency noise, pure tones and, also, for eliminating acoustic beats of two air-moving devices operating together to cool an enclosure for an impact printer.

(Image Omitted)

As shown in the schematic of Fig. 1, blower unit 10 is used for vacuum removal of ribbon debris from the face of a type band of printer mechanism. The blower unit 11 is used to draw cooling air through the carriage motors which advance print form paper. Both blower units are 3-stage vacuum/compressor blowers that exhaust filtered air through muffler unit 12. The blowers generate considerable noise at the exhaust ports. The noise emission is primarily of low frequency, ranging from 125 to 1000 Hz. Furthermore, blowers produce pure tones in the proximity of 1000 Hz, as defined by the relationship:

(Image Omitted)

Pure Tone Frequency = ( of blower blades x RPM)/60 This is also defined as the 'Blade Passing Frequency' of the blowers. The pure tones of the blowers in a printer application do not occur at the same frequency, but deviate from each other by a few Hz. because of the loading conditions while performing different functions. These pure tones of equal intensity but slightly different frequencies generate an audible beat caused by the addition and cancellation of adjacent pure tones. This form of acoustical characteristic can be annoying to machine users. Fig. 2 shows the overall noise pattern of the...