Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Chimaeric sounds reveal dichotomies in auditory perception


By Fourier's theorem1, signals can be decomposed into a sum of sinusoids of different frequencies. This is especially relevant for hearing, because the inner ear performs a form of mechanical Fourier transform by mapping frequencies along the length of the cochlear partition. An alternative signal decomposition, originated by Hilbert2, is to factor a signal into the product of a slowly varying envelope and a rapidly varying fine time structure. Neurons in the auditory brainstem3,4,5,6 sensitive to these features have been found in mammalian physiological studies. To investigate the relative perceptual importance of envelope and fine structure, we synthesized stimuli that we call ‘auditory chimaeras’, which have the envelope of one sound and the fine structure of another. Here we show that the envelope is most important for speech reception, and the fine structure is most important for pitch perception and sound localization. When the two features are in conflict, the sound of speech is heard at a location determined by the fine structure, but the words are identified according to the envelope. This finding reveals a possible acoustic basis for the hypothesized ‘what’ and ‘where’ pathways in the auditory cortex7,8,9,10.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Auditory chimaera synthesis.
Figure 2: Speech reception of sentences in the envelope and fine structure of auditory chimaeras.
Figure 3: Recognition of melodies in the envelope and in the fine structure of auditory chimaeras.
Figure 4: ‘What’ and ‘where’ for dichotic chimaeras are determined by different cues.


  1. Fourier, J. B. J. La théorie analytique de la chaleur. Mém. Acad. R. Sci. 8, 581–622 (1829).

    MATH  Google Scholar 

  2. Hilbert, D. Grundzüge einer allgemeinen Theorie der linearen Integralgleichungen (Teubner, Leipzig, 1912).

    MATH  Google Scholar 

  3. Rhode, W. S., Oertel, D. & Smith, P. H. Physiological response properties of cells labeled intracellularly with horseradish peroxidase in cat ventral cochlear nucleus. J. Comp. Neurol. 213, 448–463 (1983).

    CAS  Article  Google Scholar 

  4. Joris, P. X. & Yin, T. C. Envelope coding in the lateral superior olive. I. Sensitivity to interaural time differences. J. Neurophysiol. 73, 1043–1062 (1995).

    CAS  Article  Google Scholar 

  5. Yin, T. C. & Chan, J. C. Interaural time sensitivity in medial superior olive of cat. J. Neurophysiol. 65, 465–488 (1990).

    Article  Google Scholar 

  6. Langner, G. & Schreiner, C. E. Periodicity coding in the inferior colliculus of the cat. I. Neuronal mechanisms. J. Neurophysiol. 60, 1799–1822 (1988).

    CAS  Article  Google Scholar 

  7. Rauschecker, J. P. & Tian, B. Mechanisms and streams for processing of “what” and “where” in auditory cortex. Proc. Natl Acad. Sci. USA 97, 11800–11806 (2000).

    ADS  CAS  Article  Google Scholar 

  8. Recanzone, G. H. Spatial processing in the auditory cortex of the macaque monkey. Proc. Natl Acad. Sci. USA 97, 11829–11835 (2000).

    ADS  CAS  Article  Google Scholar 

  9. Tian, B., Reser, D., Durham, A., Kustov, A. & Rauschecker, J. P. Functional specialization in rhesus monkey auditory cortex. Science 292, 290–293 (2001).

    ADS  CAS  Article  Google Scholar 

  10. Maeder, P. P. et al. Distinct pathways involved in sound recognition and localization: a human fMRI study. NeuroImage 14, 802–816 (2001).

    CAS  Article  Google Scholar 

  11. Dodge, C. & Jerse, T. A. Computer Music: Synthesis, Composition, and Performance (Schirmer Books, New York, 1997).

    Google Scholar 

  12. Depalle, P., Garcia, G. & Rodet, X. A virtual castrato (!?). Proc. Int. Computer Music Conf., Aarhus, Denmark 357–360 (1994).

  13. Shen, C., Smith, Z. M., Oxenham, A. J. & Delgutte, B. Auditory Chimera Demo; available at 〈〉 (2001).

  14. Licklider, J. Effect of amplitude distortion upon the intelligibility of speech. J. Acoust. Soc. Am. 18, 429–434 (1946).

    ADS  Article  Google Scholar 

  15. Saberi, K. & Perrot, D. R. Cognitive restoration of reversed speech. Nature 398, 760 (1999).

    ADS  CAS  Article  Google Scholar 

  16. Nilsson, M., Soli, S. D. & Sullivan, J. A. Development of the hearing in noise test for the measurement of speech reception thresholds in quiet and in noise. J. Acoust. Soc. Am. 95, 1085–1099 (1994).

    ADS  CAS  Article  Google Scholar 

  17. Shannon, R. V., Zeng, F.-G., Kamath, V., Wygonski, J. & Ekelid, M. Speech recognition with primarily temporal cues. Science 270, 303–304 (1995).

    ADS  CAS  Article  Google Scholar 

  18. Ghitza, O. On the upper cutoff frequency of the auditory critical-band envelope detectors in the context of speech perception. J. Acoust. Soc. Am. 110, 1628–1640 (2001).

    ADS  CAS  Article  Google Scholar 

  19. Wightman, F. L. & Kistler, D. J. The dominant role of low-frequency interaural time differences in sound localization. J. Acoust. Soc. Am. 91, 1648–1661 (1992).

    ADS  CAS  Article  Google Scholar 

  20. Henning, G. B. & Ashton, J. The effect of carrier and modulation frequency on lateralization based on interaural phase and interaural group delay. Hear. Res. 4, 184–194 (1981).

    Google Scholar 

  21. Bernstein, L. R. & Trahiotis, C. Lateralization of low-frequency complex waveforms: The use of envelope-based temporal disparities. J. Acoust. Soc. Am. 77, 1868–1880 (1985).

    ADS  CAS  Article  Google Scholar 

  22. Wilson, B. S. et al. Better speech recognition with cochlear implants. Nature 352, 236–238 (1991).

    ADS  CAS  Article  Google Scholar 

  23. Rubinstein, J. T., Wilson, B. S., Finley, C. C. & Abbas, P. J. Pseudospontaneous activity: stochastic independence of auditory nerve fibers with electrical stimulation. Hear. Res. 127, 108–118 (1999).

    CAS  Article  Google Scholar 

  24. Litvak, L., Delgutte, B. & Eddington, D. Auditory nerve fiber responses to electrical stimulation: modulated and unmodulated pulse trains. J. Acoust. Soc. Am. 110, 368–379 (2001).

    ADS  CAS  Article  Google Scholar 

  25. Greenwood, D. D. A cochlear frequency-position function for several species—29 years later. J. Acoust. Soc. Am. 87, 2592–2604 (1990).

    ADS  CAS  Article  Google Scholar 

  26. Ville, J. Théorie et applications de la notion de signal analytique. Cables Transmission 2, 61–74 (1948).

    Google Scholar 

  27. Troullinos, G., Ehlig, P.,,Chirayil, R., Bradley, J. & Garcia, D. in Digital Signal Processing Applications with the TMS320 Family (ed. Papamichalis, P.) 221–330 (Texas Instruments, Dallas, 1990).

    Google Scholar 

  28. Hartmann, W. M. & Johnson, D. Stream segregation and peripheral channeling. Music Percept. 9, 155–184 (1991).

    Article  Google Scholar 

Download references


We thank C. Shen for assistance with data analysis and J. R. Melcher and L. D. Braida for comments on an earlier version of the manuscript. A.J.O. is currently a fellow at the Hanse Institute for Advanced Study in Delmenhorst, Germany. This work was supported by grants from the National Institutes of Health (NIDCD).

Author information

Authors and Affiliations


Corresponding author

Correspondence to Bertrand Delgutte.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Smith, Z., Delgutte, B. & Oxenham, A. Chimaeric sounds reveal dichotomies in auditory perception. Nature 416, 87–90 (2002).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing