About the article

Stereo Robot Ears

Stereo Robot Ears

Service robots of the future will most likely need to act on spoken commands and be able to recognise voices. This article takes a look at one aspect of this behaviour namely locating the position of a sound source using the cross-correlation function. A technique is developed which drastically cuts down on the number crunching so that even a basic microcontroller fitted with binaural sensors can pinpoint a continuous audio signal with an accuracy of just 10 degrees.

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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Component list


R1,R5,R12 = 47kΩ

R2 = 33kΩ

R3,R10 = 22kΩ

R4,R11 = 1kΩ

R6,R9,R13,R16,R18,R19,R20 = 10kΩ

R7, R14 = 2kΩ2

R8, R15 = 100kΩ

R17 = 100kΩ preset

Rx = 100kΩ



C1,C2,C3,C4 = 1µF 16 V

C5 = 22µF 16 V

C6 = 100µF 16 V

C7,C8 = 100nF

C9,C10 = 22pF



IC1 = LM324

IC2 = PIC16F88, programmed, order code 060040-41 from Elektor SHOP


Q1 = 20MHz quartz crystal

DIL14 socket

DIL18 socket

SL1,SL2,(SL4),SL5,SL6,SL7 = 2-way SIL pinheader (SL4 bridged with a 100k resistor, see text)

SL3 = 6-way SIL pinheader

JP1,JP2 = jumper

MicR, MicL = CZ034 electret microphone insert

PCB, ref. 060040-1, free artwork download

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