Correlogram Introduction

This web site is a repository for information about the correlogram. The correlogram is a model of auditory perception that explains how the auditory system might process and understand the temporal information in the audio signals we hear. The auditory correlogram was "invented" by J. C. Licklider in 1951, but at the time he could only draw pictures of the representation. More recently the correlogram was popularized by Richard F. Lyon, Malcolm Slaney and Roy Patterson to model and explain pitch perception. Many of the examples presented here were first presented in the Apple Hearing Demo Reel.

To read more about what a correlogram is, and how it is computed go to this page about the correlogram, or to the bibliography.

The web link below (Leonardo) leads to a simple example of the correlogram, showing how it represents sounds along two axes: frequency and time delay.

Correlogram Examples

These examples demonstrate the basic properties of a correlogram.

ASA Examples

The Acoustical Society of America (ASA) created a wonderful collection of auditory demonstrations. Some of these demonstrations are useful when thinking about the temporal properties of perception. If you are interested in sound you should have a copy of this audio CD. Ordering information is available from the ASA.

Auditory Image Examples

Most of the correlograms presented here were computed using autocorrelation. While this is a straight forward mathematical algorithm, it is certainly not how the brain would do the calculation. Roy Patterson's Auditory Image Model (AIM) proposes a biologically more realistic computational implementation, based on strobed temporal integration (STI). The videos in this section were computed using an early model of STI.

Miscellaneous Examples

These videos show simple examples from Lyon's cochlear modeling. This cochlear model is the basis of the (autocorrelation) correlogram videos shown here. We also have a three-panel correlogram showing the difficulty of sound separation, and a video from an early VLSI chip that computed the correlogram.