Listen Through Wall Device

The listen through wall device is a special amplifier that will pick up sounds through solid barriers, such as walls, partitions and windows that it would normally have not been possible to hear purely with the human ear.

Developed from Automotive Engineering Concepts

The forerunner of the listen through wall device was originally engineered as an automotive tool. Mechanics used high-gain acoustic sensors to analyse noises deep inside vehicle engines, pinpointing mechanical faults before dismantling complex machinery.

Over time, security specialists adapted this sound-transmission technology for covert surveillance. By refining the acoustic sensor and tuning the amplifier, engineers created a professional listen through wall device designed to translate micro-vibrations through solid architectural structures into clear, audible sound.

Sound Amplification & Adjustable Audio Controls

This specialist listening device features an ultra-sensitive ceramic contact microphone. Positioned against a wall, the sensor detects minute structural vibrations caused by room audio and routes them straight into the high-gain amplifier.

To optimise clarity, the device includes independent treble and bass equalisation controls. Adjusting these filters reduces background hum and low-frequency resonance, allowing you to isolate human speech clearly through brick, concrete, glass, or wooden partitions.

Versatile Barrier Operation & Magnetic Mounting

For optimal acoustic transfer, the contact sensor works best on solid structures up to 300 mm (12 inches) thick. It handles heavy brickwork, solid concrete, ceilings, and double-glazed windows with exceptional clarity, while also achieving reasonable results through standard cavity walls.

The acoustic microphone features an integrated magnetic base, making it effortless to attach to steel beams, metal partition frames, or pipework. When deploying the listen through wall device against non-magnetic surfaces like plasterboard, low-tack adhesive putty can be used to hold the sensor flush.

Earphones Supplied – External Voice Recorder Connection

Real-time audio monitoring is conducted through the supplied high-clarity stereo earphones. The amplifier housing also features an auxiliary audio-out port, enabling seamless connection to an external digital voice recorder for long-term evidentiary logging.

Connecting an external recorder allows you to archive audio while monitoring live. A standard audio patch lead is included, which pairs perfectly with our Digital Voice Recorder Pro or Voice Recorder Ultimate modules without needing specialist adapters.

Battery Powered for Portable Field Use

Designed for complete mobility, this compact listen through wall device operates on a standard 9V (PP3) alkaline battery. A fresh battery provides up to 24 hours of continuous operational monitoring in the field.

For long-term surveillance operations, upgrading to a high-capacity lithium 9V battery will extend runtime significantly. Alternatively, standard rechargeable PP3 batteries can be swapped in to keep operational costs low during frequent, repeated deployments.

Can I connect a digital voice recorder to capture what the device hears?

Yes. The unit includes a 3.5mm audio patch lead to connect directly to external digital recorders. Depending on your recorder’s input jack, a standard plug adapter may occasionally be required.

How can I attach the contact microphone to a wall for hands-free listening?

While the microphone features a magnetic base for steel surfaces, it can be attached to plasterboard or brick using low-tack adhesive putty (Blu-Tack) around its edges, or secured flush using heavy-duty tape.

Could I attach this to the outside of a car to listen to conversations inside?

This is not recommended. The unit is not waterproof, and road vibration would disrupt the audio feed. Placing a dedicated covert voice recorder inside the cabin is a far more reliable solution.

What is the maximum wall thickness the listen through wall device can penetrate?

The acoustic sensor works best on solid structures (such as brick, concrete, or stone) up to 300 mm (12 inches) thick, as well as standard interior cavity walls and partitions.

How do the treble and bass controls help improve sound clarity?

The equaliser dials allow you to filter out background hums and structural low-frequency rumbles, helping to isolate and clarify human voice frequencies on the other side of the barrier.

Is there any risk of sudden loud noises hurting my ears while listening?

Because contact sensors pick up surface vibrations, dragging or tapping the microphone while turned on creates loud feedback. You should always position the sensor before putting on the earphones and adjusting the volume.

• The device is strictly powered by a standard 9V (PP3) battery. There is no facility to connect it to a mains electricity supply.
• While standard 9V alkaline batteries are widely available, using a high-capacity lithium 9V battery will provide up to three times longer operational life.
• The contact sensor features a built-in magnet for metal surfaces. For mounting on non-magnetic walls, low-tack adhesive putty (such as Blu-Tack) or heavy-duty tape can be used to hold the sensor flush.
• This unit performs best on dense, solid structures such as solid brick, poured concrete, stone, or glass. It is less effective on hollow cavity walls with large insulation gaps or soft stud partitioning.
• While real-time audio is monitored directly through the supplied earphones, an external voice recorder (sold separately) is required if you intend to archive or save your audio files.
• Because the contact microphone is exceptionally sensitive, touching, dragging, or adjusting the sensor while in use will create loud surface feedback. The sensor must remain completely still while listening.

• Converts minute structural surface vibrations caused by sound waves into clear, audible room audio.
• Effectively monitors acoustic activity through solid brick, concrete, plasterboard, glass, and cavity walls up to 300 mm thick.
• Adjustable bass and treble controls allow operators to isolate vocal frequencies and filter out ambient structural noise.
• Integrated magnetic contact head permits quick, hands-free mounting onto metal frames, steel joists, and pipework.
• Dedicated 3.5mm line-out port enables simultaneous live monitoring and audio archiving via an external digital recorder.
• Functions as a surveillance tool or an industrial diagnostic device for tracking fluid flow in pipes and analyzing machinery faults.
• Includes comfortable stereo earphones for zero-leakage, covert real-time listening in sensitive environments.
• Operates independently on standard 9V battery power without requiring access to mains electricity.

• Barrier Thickness Capacity: Up to 300 mm (12 inches)
• Compatible Barrier Materials: Brick, concrete, stone, plasterboard, wood, glass, and metal pipes
• Microphone Type: High-sensitivity ceramic contact piezo sensor
• Sensor Mounting: Magnetic base (adhesive mount compatible)
• Audio Controls: Independent Bass and Treble equalizer dials, Master Volume control
• Outputs: 3.5mm Headphone Jack, 3.5mm Line-Out Recording Jack
• Power Source: 1× 9V (PP3) Battery (Alkaline included; Lithium/Rechargeable compatible)
• Battery Operating Life: Up to 24 hours continuous use (Alkaline)
• Dimensions (Amplifier Unit): 110 mm × 65 mm × 25 mm
• Weight: Approx. 180 g (including battery and sensor)

• High-Gain Listen Through Wall Device Amplifier Unit
• Magnetic Ceramic Contact Microphone Lead
• Stereo Listening Earphones
• 3.5mm Audio Output Patch Lead (for external recorder connection)
• 1× 9V (PP3) Battery
• Detailed Instruction Manual
• Support by Email or Phone if Required