I need Echo cancellation readymade module for HW

HI,

In my VOIP application. i have used audio amplifier and Mic (condenser type) for open environment. But the Mic has pickup speaker signal and it create ECHO issue.

i want to arrest echo problem in hardware level. So please suggest Echo cancellation or suppressor ready made module / chip

My impression when talking on my cellphone, is that it allows the louder signal to get through. If I'm talking louder than the other person, he hears me. His mic shuts off. I guess that is what prevents echo.

It may be similar to squelch. (Squelch is commonly used to quiet noise in radio conversations, except when someone broadcasts a signal.)

A two-way squelch circuit will detect which signal is louder, incoming or outgoing. It will turn on the louder signal, and shut off the softer signal. It will require a few components.

panneerrajan said:

HI,

In my VOIP application. i have used audio amplifier and Mic (condenser type) for open environment. But the Mic has pickup speaker signal and it create ECHO issue.

i want to arrest echo problem in hardware level. So please suggest Echo cancellation or suppressor ready made module / chip

Click to expand...

Modems have echo suppression for one inline echo that allows maximum bit rate, two echoes are not commonly suppressed and data rate reduces.

VOIP must have local echo suppression and go to half duplex if feedback of local source comes from remote by signal analysis.

For local feedback, best start is a noise cancelling near-field mic , chosen by attenuation at distance of speaker. Next cancellation method is fixed delay and attenuation of inverted signal by pulse injection and analyze response for DSP cancellation. Simplest cancellation is called "side-tone" cancellation is not reliable if speaker level is non-linear. Better method is partial attenuation operation sending if mic level is low. Many other algorithms exist to minimize echo or minimize bandwidth used.

The method chosen determines complexity of signal process you plan to handle.

1st determine where echo is caused then decide which type of Echo cancellation to use with an algorithm to correctly take away a portion of the transmitted signal from the return signal to eliminate the echo.

- - - Updated - - -

VOIP server can do some.

https://www.voipmechanic.com/correcting-echo-asterisk.htm

Overview details
https://www.cisco.com/c/en/us/td/docs/ios/solutions_docs/voip_solutions/EA_ISD.html#wp1041385

Hi,

Thank you for your support,

Hi,
we are making VOIP type call box with microprocessor based design and its not have local echo suppressor. So we are looking ready made Chip or Hardware module to arrest the Echo in hardware level.

May be this module need to interface at Mic receiving point

if you know any ready module Please suggest me
Thank you
Panneer

I spent years working with a team from a major telecoms company who were trying to do this purely electronically and I think I can say from their frustration, it isn't possible.

The real issue is the echo is not a replica of the original, apart from the delay, it is distorted in the frequency and time domain by the return route from the far end. You are asking for a device that can analyze your outgoing speech and the incoming speech, find similarities and subtract the result from the received audio, it just isn't practical to do, especially in real time.

Things you can try:

1. as mentioned earlier, a noise cancelling microphone to eliminate some of the unintended pick up.
2. a system like 'anti-vox' used in radio comms where the received level is used to desensitize the microphone amplifier.
3. a ring modulator and LF oscillator (<10Hz) to pitch shift the microphone signal slightly. This doesn't stop the echo but it helps to stop accoustic feedback (howling).
4. an electronic add and invert system to mix the incoming and outgoing signals (like a POTS hybrid network) but you will need complex filtering and the results may be different from one call to another, possibly making the situation worse on some calls.

Brian.

Dear Mr. Brian,

Thank you for your clarification

If you have idea in ring modulator and LF oscillator, Pls. share the details. I will try that concept

Thank you
Panneer

It was about 15 years ago so I can't remember all the details but I think they used an MC1496 with an LO of about 5Hz. All it had to do was shift the audio pitch slightly to break the dominant pole in the feedback path. The shift was small enough that it was hardly noticed in normal speech but it had a dramatic effect on reducing accoustic feedback. It will not do anything to stop long echo though!

Brian.