Echo and Reverberation
by Atlanta Signal Processors, Inc.

Software Overview

The TMS320C3x Echo and Reverberation software is an implementation of the tap reverberator 
described by James Moorer in "About This Reverberation Business." Echo and reverberation are the 
addition of audio effects to simulate the sound created in a variety of different rooms, similar to 
the capability to simulate a concert hall that currently exists with many commercially-available 
amplifiers. The reverberator consists of four sections. The first is an early reflection buffer 
that has the option of 18 or 6 early reflections. The 18 reflections correspond to three 
reflections for each of the 6 walls and is a more natural sound. The second section is six parallel 
comb filters. Third, is an all-pass filter which increases the echo density by adding reverberation 
to the already reverberated signal. Finally, a delay line is used to synchronize the output of the 
early reflection buffers with the output of the all-pass filter.
Applications that may utilize echo or reverberation software include multimedia systems requiring 
special audio effects or any audio system that requires the enhancement of sampled audio data.

Features and Benefits

•	Code is C callable, relocatable, and SPOX compatible
•	Six wall implementation (four walls, floor, ceiling)
•	Variable number of reflections, 6 or 18 on a single TI TMS320C3x DSP

Processor and System Specifications

•	Memory requirement:
Program memory:
390 words external, 275 words internal. 
Data memory: 8,192 words.
Processor loading (33-MHz TMS320C3x with zero-wait-state SRAM)
100% for six walls, 18 early reflection taps at 25.5-kHz sampling rate
•	Ready to run on the Elf DSP Platform from Atlanta Signal Processors
•	Portable to any TMS320C3x target platform

Usage Limitations or Performance Considerations

•	18 reflection maximum sampling rate:
51-kHz mono, 25.5-kHz stereo
•	Six reflection maximum sampling rate:  70-kHz mono, 35-kHz stereo

Algorithm Verification

•	There are no international standards for this algorithm. However it has been extensively tested.

Availability

•	Written by Texas Instruments and available now through Atlanta Signal Processors.

Company Background and Contact Information

Atlanta Signal Processors was founded in 1981 by Ronald W. Schafer, Thomas P. Barnwell III, and 
Russell M. Mersereau, three Professors of Electrical Engineering at the Georgia Institute of 
Technology with over 80 years of experience in the field. The company has focused its efforts on 
developing tools for professional signal-processing design engineers and now offers digital 
signal-processing hardware and software products to DSP designers worldwide.

Contact:	Atlanta Signal Processors, Inc.
		1375 Peachtree St. NE, Suite 690
		Atlanta, Georgia  30309-3115
		(404) 892-7265
		Fax: (404) 892-2512
		e-mail: aspi@aspi.com