Vehicle voice amp/intercom

Maybe something off-the-shelf like used at drive up food ordering stations? ...Jim Thompson

You'd need two amps, one going forward, one going back, to separate the speakers.

Active feedback cancellation may be necessary, but maybe not. Certainly things would go much better with it.

It would _really help_ to use short-range microphones that you'd have to get your mouth _close_ to to talk -- but that would be difficult both for the driver and for a seriously mobility impaired passenger.

Interesting problem.

Lots more acoustic isolation than in a van, though.

There are in-vehicle voice communication systems comprised of multiple speakers and mikes. Those systems are expensive as they do pretty heavy DSP for feedback suppression and acoustic beamforming. The systems require professional installation as they have to be tuned for every particular setup.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

How do they do with the change in environment from an empty van to one with a person in a wheel chair?

Don't know. Reacting to the sudden changes of environment is one of the challenges of acoustic echo suppression; office systems do reasonably well. Vehicle systems use side information (doors open, etc.).

VLV

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I have a totally sideways approach for you. Bluetooth headsets and a = serverlet=20 in the bus.

Thanks for the ideas so far guys. I'd searched for commercially available systems and found nothing, so I'd be interested in any product names.

I'd also found this circuit

Midge.

I have a totally sideways approach for you. Bluetooth headsets and a serverlet in the bus.

I assume this is, for example, used to cart folks from an assisted living center (nursing home, etc.) to doctor appointments, shopping, etc.? I.e., it is *not* part of a "mass transit" system.

As such, it isn't traveling a prescribed "route" where a passenger could just *signal* "I'd like to get off at the next stop". I.e., the passenger *needs* to communicate with the driver...

But, only because you don't want to where a helmet? I.e., could you cannabilize such a system and just mount the individual transceivers "in appropriate locations" so driver and passenger can successfully utilize them? For example, the wheelchair bound passenger(s) have *fixed* locations within the vehicle that are designed to accommodate their chairs. So, a speaker/mic can be located proximal to the chair(s). Likewise, the driver tends to have a fixed location so you could mount "his end" near the driver's seat.

(note that a *wired* solution might be better and could accommodate more locations -- e.g., two or more chairs plus the driver)

Use highly directional microphones. Point them away from the speaker(s) to eliminate feedback.

I'm not sure why you rule out PTT as the button *could* be located close to the occupant -- even on an umbilical for the duration of such a ride (?)

Thanks for the suggestions - I'll look at the Mics. This is just normal everyday use by husband/wife. The vehicle is a 7 seater Ford Galaxy people carrier. The wheelchair is where the back two seats would normally be. They can shout at each other (!) but obviously can't have a normal conversation at higher speed.

The lady in the wheelchair has MS which attacks the nervous system. At the moment she might just be able to operate a button but that can't be guaranteed in the future. It is also why she will struggle to make herself heard from that far back in the vehicle. Obviously, you wouldn't really want PTT for the driver either.

Midge,

Just get a pair of small airplane headsets and an airplane intercom.

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You might try the BlueAnt InterPhone, rather pricey but it proves that = the=20 tech exists.

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Cell phones with Bluetooth headsets and an unlimited intra-provider plan?

Since the "users" don't vary, why not just get a pair of Plantronics (et al.) headsets and *wire* them together with a small opamp. Add a bit of sidetone if you want (an extra set of R's?). The driver (husband) can place the headset on the passenger (wife) when he straps her chair in place. He can then place *his* on when he gets into the driver's seat. Anything/everything said by either will be heard by the other. The microphones' proximities to their mouths will cut down on extraneous noise. The presence of each of their *skulls* between the earpieces and mics will eliminate feedback.

No brainer. :> Headsets should be easy to come by (I see them discarded pretty frequently). No need to fuss with PA's, wireless, etc.

NASCAR drivers have a PTT control and manage to avoid (most?) accidents while using it :>

:Have a bit of an unusual requirement and I confess my electronics design :knowledge is very basic digital and pretty much nil analogue, but I wondered :how easy this would be to do...... : :The scenario is a large people carrier converted to take a wheelchair bound :passenger in the back - but when vehicle is on the move, driver can't quite :hear passenger and vice versa. : :This sort of thing isn't uncommon when considering rider/pillion on a :motorbike OR between driver and co-driver in a race/rally car - but helmets :and headset intercomms used in these applications aren't suitable in this :case. : :So what I had in mind is something like a mini-PA system - just a few watts :amp into a single speaker, but with the possibility of feeding two :microphones into it (lets assume we don't allow them to talk over each :other - but otherwise, permanently open in operation). : :PTT isn't an option so needs to be handsfree VOX activated or have very :effectively noise supression to get rid of the road/wind and other vehicle :noise when not talking. In such a confined space, would also need to be very :good at stopping feedback through the active microphone. : :Any thoughts/ideas appreciated. : :TIA, Midge :

Perhaps this off-the-shelf system would be suitable.

Of course, you would need to replace the supplied mains psu with something equivalent powered from th vehicle battery.