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In the office and home computing environments, printer impulsive noise has become a significant contributor to user perceived quality or lack thereof, and can affect the user’s comfort level and ability to concentrate. Understanding and quantifying meaningful metrics for printer impulsivity is becoming an increasingly important goal for printer manufacturers. Several methods exist in international standards for measuring the impulsivity of noise. For information technology equipment (ITE), the method for detection of impulsive noise is provided in ECMA-74 and ISO 7779. However, there is a general acknowledgement that the current standard method of determining impulsivity by simply measuring A-weighted sound pressure level (SPL) with the impulsive time weighting, I, applied is inadequate to characterize impulsive noise and ultimately to predict user satisfaction and acceptance. In recent years, there has been a variety of new measurement methods evaluated for impulsive noise for both environmental and machinery noise. This paper reviews several of the available metrics, applies the metrics to several printer impulsive noise sources, and makes an initial assessment of their correlation to the subjective impressions of users. It is a review and continuation of the work presented at InterNoise 2005 (Baird, Bray, and Otto).

The conventional spectral weightings applicable to sound pressure [dB(A), etc.] are fixed in spectral shape and intended for use over certain ranges of unweighted sound pressure level: for example, the A-weighting from threshold of hearing up to 65 dB(SPL). In general, these weightings’ spectral shapes match the sensitivity of hearing as a function of frequency within “use-level” ranges, although the strong effect of the cavum conchae resonance of the ear, apparent in the equal-loudness contours of ISO 226, is not considered except in the rarely Used D-weighting. Particularly for sounds with tonal content and within the general level range of the A-weighting, the authors propose a new spectral weighting assembled from the Phon values of the complete set of equal-loudness contours calculated for each frequency within the human auditory range. It will be shown that although giving values similar to those of the A-weighting, the dB[EQL] or equal-loudness weighting is situation dependent rather than fixed, and better represents subjective impressions at all frequencies. Although based on perceived loudnesses, the dB[EQL] sound pressure weighting is not a specific loudness measurement, does not consider critical band formation, and does not yield masking or psychoacoustic loudness data.