Circuit trigger on specific preset sound

[vygram]

I am currently working on a project that require me to trigger a relay when a specific sound is played through the set device. The general idea of a sound activated switch I have, but it triggers the relay on all sound that is played.

I circuit must trigger only when the specific sound (probably stored in memory) is played. An help or a nudge in the right direction will be appreciated

 

[duke37]

You will need to define the type of sound that you wish to use.
This could be frequency, amplitude, harmonics etc.

It appears that you are using amplitude only, this is the easiest to do.
Analysing complex sound can take a lot of calculations. Look up fast fourier analysis.

 

[vygram]

The unit basically works the same way a two-way radio would. Normally it is just chatter that is coming through, but as in a two-way radio, when a specific melody (in this case sounds like a desk phone) is played, the relay must trigger.

 

[AnalogKid]

Tone activated switching is very different from, and much easier than picking a particular sound out of voice audio (for example). This is an outgrowth of touch-tone dial circuits. Signetics (then Phillips then NXP?) and National (now TI) used to make a cute little phase-locked loop tone detector, the NE567 or LM567. App notes for that part should give you a start.

ak

 

[duke37]

An FM radio will produce a loud hiss when no signal is received. The muting is turned off to when this hiss dissapears.
Radio amateur repeaters use a tone which is below the audio range to activate them. Different repeaters use different tones so that access can be selective.

 

[Colin Mitchell]

I have a tone operated circuit using a PIC chip.
You just need to tell the chip what frequency it needs to listen to and it activates an output.