Jules, post: 465538, member: 52053 wrote: We need a device for our car - To block any listening devices E.g. Parabolic dish.

We believe some form of ultrasonic speech jammer will do the trick - https://www.detective-store.com/portable-audio-jammer-komar-sel-310-for-securing-conference-rooms--1745.html or https://www.brickhousesecurity.com/counter-surveillance/dual-channel/

We also need one for room protection, something to cause microphone distortion. E.g Room meetings, we were thinking about getting creative and using a subwoofer to mask our conversations.

I'm not sure why you believe that the REI noise generator from Brickhouse is ultrasonic - its specifications say "125 Hz - 4 kHz". I don't think I could hold any sort of private communication in a room with that thing sounding off. Mind you, an electrical power input spec of 12W offers an indication of how much acoustic power it can produce.

Speech can be intelligible in a very restricted bandwidth. The traditional frequency range for telephones is 300Hz - 3KHz, and it can be squeezed to much less than that and still be recognisable. The typical frequency range of standard low-cost microphones might be 50Hz - 18KHz, so putting up puny walls of infrasound (<20Hz) or ultrasound (>20KHz) would have little effect on them.

All in all, devices that attempt to mask the intelligibility of conversation tend to cause more distress to the speakers than to any equipment that may be monitoring them. Hollywood makes great play of characters that want to hold a secret conversation turning a radio or gramophone up loud, but there's precious little science behind it. What that would do is draw external attention to the likelihood that some private conversation is taking place, and that it could be worth using standard espionage gear to listen to it.

I'm not trying to pooh-pooh your intentions, which are doubtless laudable, but I do think you need to look at these acoustic security devices with your eyes wide open. I would think the sellers make a lot of money by preying on their customers' feelings of insecurity.

Thankyou for the information, I am happy to receive any advice honestly. It looks like I don't know much sadly, if you don't mind me asking, what would you recommend?

Realistically - there is solid science to help you. There are all sorts of commonly quoted products for eavesdropping and they all rely on either direct capture of changes in pressure. The cleverest ones being able to detect minute movement of glass in windows. The voice makes the glasswork wobble minutely, and shining a laser on the glass can produce reflections that vary in sympathy. Clearly to stop eavesdropping requires the transmission of these vibrations to be stopped. In fact, it's very much the same problem we have trying to keep sound in a studio and stopping it leaking out, and stopping traffic noise leaking in. In general the solution is to prevent transmission - we use mass and separation as our usual tools. So thick, sold and heavy walls, so sympathetic vibration is minimal, air gaps with no physical connection so the vibrations that one boundary allow free then have to travel through an air space, then be strong enough to excite the next boundary to physically move. To do it for music is hard because bass guitars, synths and drums are powerful and very low, making the sympathetic excitement of two non-contact surfaces possible. Your problem is less critical - we're looking at what? 300-3000Hz in the main - perhaps a bit higher and lower, and speech is naturally quiet. You can build speech proof spaces with quite mild transmission techniques and double glazing. I certainly would not like to work in these spaces though. You need extra ventilation to shift the heat because you need to seal the space.

I remember speaking to a policeman once who had been involved in having to talk in a police station with sealed windows and a decent distance to the paparazzi across the road. They all got read the riot act for the leaks. It turned out all the newspapers had done was give a lipreader a pair of binoculars!

It's perfectly possible to construct simply a room inside your building where sensitive talks can be held - a solid door and no windows and perhaps making sure it's not on an outside wall will do the trick. Just ban sensitive conversation from any other rooms.

The issue in this case with an isolation room is in fact the ventilation. Building code requires fresh air be drawn from the outside, you can't use an adjacent room's fresh air.

So you will have a vent the sends and feeds to/from the outside.

While you could use a mesh screen to limit access, there is no way to completely seal it off while maintaining ventilation. So while there are methods to prevent sound transmission, securing it from devices that may be placed in the vent/ducting is more challenging, since regardless of how long and windy the path of the duct, it ultimately has to come from the exterior of the building.

Jules, post: 465540, member: 52053 wrote: Thankyou for the information, I am happy to receive any advice honestly. It looks like I don't know much sadly, if you don't mind me asking, what would you recommend?

The best security starts and ends with you. If you have a situation where you are worried about data loss through eavesdropping then you need to tighten down where and when (and how) you communicate. If the car can't be secured then you need to stop talking there. You need a special room that you can sweep (and secure) so you know you are safe(er) than the car where you are targetable to all kinds of things... but you need first to manage the human element. Look at all your practices and make changes/develop best practices.

Nowadays I suspect that allowing a room full of iPhones sending their data back for Facebook and google is more of a worry. If you discuss your hot subject, wait a few minutes and Facebook will suggest an alternate supplier for it?