Skip to content


  • Research Article
  • Open Access

The Acoustic and Peceptual Effects of Series and Parallel Processing

  • 1Email author,
  • 1 and
  • 1, 2
EURASIP Journal on Advances in Signal Processing20092009:619805

  • Received: 8 December 2008
  • Accepted: 5 August 2009
  • Published:


Temporal envelope (TE) cues provide a great deal of speech information. This paper explores how spectral subtraction and dynamic-range compression gain modifications affect TE fluctuations for parallel and series configurations. In parallel processing, algorithms compute gains based on the same input signal, and the gains in dB are summed. In series processing, output from the first algorithm forms the input to the second algorithm. Acoustic measurements show that the parallel arrangement produces more gain fluctuations, introducing more changes to the TE than the series configurations. Intelligibility tests for normal-hearing (NH) and hearing-impaired (HI) listeners show (1) parallel processing gives significantly poorer speech understanding than an unprocessed (UNP) signal and the series arrangement and (2) series processing and UNP yield similar results. Speech quality tests show that UNP is preferred to both parallel and series arrangements, although spectral subtraction is the most preferred. No significant differences exist in sound quality between the series and parallel arrangements, or between the NH group and the HI group. These results indicate that gain modifications affect intelligibility and sound quality differently. Listeners appear to have a higher tolerance for gain modifications with regard to intelligibility, while judgments for sound quality appear to be more affected by smaller amounts of gain modification.


  • Parallel Processing
  • Intelligibility Test
  • Series Processing
  • Acoustic Measurement
  • Speech Quality

Publisher note

To access the full article, please see PDF.

Authors’ Affiliations

SLHS-Speech, Department of Speech, Language, and Hearing Science, University of Colorado at Boulder, 409 UCB, Boulder, CO 80309, USA
GN Resound, 2601 Patriot Blvd., Glenview, IL 60026, USA


© Melinda C. Anderson et al. 2009

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.