Acoustic Safe ASU-20, light wood color

Acoustic Safe ASU-20, light wood color

Noiseless Acoustic Safes 

Ultrasonic acoustic safes ASU-20 and ASU-20A are designed to protect speech and any other acoustic information from leakage through smartphones, tablets and headsets. 

The acoustic safe is a box made of natural wood with a built-in ultrasonic acoustic noise generator. The dimensions of the box allow to place up to 20 phones in it. Thanks to the use of powerful noise emitters in close proximity to the microphones of protected devices, reliable suppression of any acoustic information is ensured.

Unlike passive acoustic boxes and jammers, that turn on suppression only when the phone is active, a constantly working jammer in the ultrasonic acoustic safe guarantees complete blocking of smartphones' and headsets' microphones. Ultrasonic energy density inside the closed volume of the acoustic safe reaches up to 300 J/m³, providing very efficient blocking. Almost all of the ultrasound is absorbed by the body of the acoustic safe or reflected inwards. When the lid is closed, the box works silently. Reception of incoming calls and messages is not blocked. When phones are in the box, sounds of calls and messages are heard from outside, and all external sounds inside the box are muted. The operating time of the acoustic safe is not limited

 Acoustic safe ASU-20A in a negotiation room

 Acoustic safe is a necessary thing to ensure the confidentiality of negotiations

Why is It Relevant Today?

In the era of push-button telephones, listening to a room through a telephone microphone seemed like a paranoid idea. With the advent of smartphones, this has become a reality.

The link shows various experiments proving that many popular apps use a microphone to listen in on conversations around them and then showing relevant ads. How else the obtained information is used - one can only guess. Facebook denies eavesdropping on users, but there have been reports that Facebook has been harvesting audio from some Messenger voice chats and paid contractors to listen and transcribe it. The head of Facebook confirmed this information. Acoustic data was collected not only by Meta, but also by Apple, sharing the data with third parties. In 2019, after the scandal, they apologized and promised not to do it again. Whether the promise was kept is unknown. Apparently, Google also did not stand aside. A group of scientists from Northeastern University (Boston, USA) in 2018 analyzed 17,260 applications from Google Play and found that 9,100 of them had access to the camera and microphone, and several hundred of them were constantly transmitting the user's media information to their servers. 

In addition, there are dozens of programs for Android and iOS that anyone can purchase and use to covertly listen to a room through a smartphone. The search query "listen to phone surroundings" produces a large number of links to such applications. Among them, it is worth mentioning the infamous Pegasus spyware, which was used to spy on politicians and journalists and, apparently, after various modifications aimed at increasing the obscurity of its work, continues to be used.

Conversations may not be transmitted immediately, but recorded in a phone's memory and only then (when network available) be uploaded to the attacker's server. In such a situation, conventional cell phone jammers and Faraday cages are not effective. The best solution is to securely block the microphones of phones and headsets during conversations to prevent leakage of any acoustic information.

Some acoustic safes have disadvantages: 1. Many models use audible noise (noise in the audio range) to create interference. The noise during their operation is heard from the outside and irritate persons during prolonged use. If the sound isolation is so good that the noise is not heard, then the sounds of calls and incoming messages are not heard. 2. There are models (both sonic and ultrasonic) that use stationary white or pink noise to create interference (audible as a uniform hiss). Modern software tools can filter out such noise. 3. Some models turn on interference only at the moment of detection of transmission of some information. This approach is not effective, because the phone can first write data to its memory and only then transmit it.

Our acoustic safes use ultrasonic pseudo-random frequency hopping signal (floating spectrum noise) to make the interference and do not have the above disadvantages.

The question often arises: why ultrasonic jammers (usually installed under the ceiling) designed to suppress voice recorders in rooms do not provide 100% protection and suppress far from all types of devices, while we promise reliable microphone suppression of any device in our acoustic safes? It's all about the protected volumes and the ultrasound energy density. When a jammer operates in an open volume of a room, ultrasonic energy is distributed throughout the entire volume of the room. For example, a relatively small office measuring 5x5 meters with a ceiling height of 3 meters has a volume of 75m³, which is 75,000 liters. At the same time, the volume of the acoustic safe is only a little over 3 liters, and all the ultrasonic energy acts in this volume. Thus, the ultrasonic energy density inside the acoustic safe is thousands of times higher, which ensures reliable blocking of any microphones.

How to Use the Acoustic Safe? 

1. Connect the power supply to the connector on the back of the box.
2. Open the box, put phones and headsets in there. If you have ASU-20, press the red button to turn on the noise generator. ASU-20A turns on the noise generator automatically when the lid is closed.
3. After negotiations, take out the phones and turn off the device by pressing the red button (ASU-20) or just leave the box open (ASU-20A).

Available Colors 

On the photo, we tried to convey the colors of the boxes as accurately as possible. However, keep in mind that the color tone may vary slightly from box to box. The following colors are available: dark wood, red wood, light wood and oak. Please check the availability of oak color. 

Acoustic safes color options

Color options

Contents of Delivery ASU-20 / ASU-20A

1. Acoustic safe – 1 pcs
2. Power supply with a key for power switching – 1 pcs
3. Passport of the product – 1 pcs
4. Packing – 1 pcs

Brief Specifications ASU-20 / ASU-20A

  Total power of ultrasonic emitters:  up to 2 W
  Type of interference:  ultrasonic pseudo-random frequency hopping signal (floating spectrum noise)
  Switchable power levels:  5
  Operating mode:  continuous
  Turn on/off:  manual (ASU-20) / automatic (ASU-20A)
  Number of protected phones:  up to 20
  Case material:  natural wood
  External dimensions / internal dimensions of the acoustic safe:  359x244x59 mm / 330x200x50 mm
  Packing dimensions and weight with packing:  391x252x60 mm, 1.3 kg

Information Security of the Acoustic Safe Itself

It's not a secret that one of the best places to embed eavesdropping devices is the information security devices themselves. The laconic design of our acoustic safes makes it difficult to install any additional electronic blocks. It is possible to supply safes with open covers of electronic compartments for inspection by your security service. The manufacturer's warranty does not cover product failure during inspection.

Electronic compartment of ASU-20A

Electronic compartment of ASU-20A

Manufacturer's Warranty 

The manufacturer guarantees the correct functioning of the product, providing that the rules of storage and operation are observed. Warranty period is 3 years from the date of sale. 


 Acoustic Safe ASU-20 "Safebox"

Acoustic Safe ASU-20 "Safebox" 


Acoustic ultrasonic safe ASU-20 is designed to protect speech and any other acoustic information from leakage through smartphones, tablets and headsets. Protects up to 20 phones simultaneously.

Acoustic Safe ASU-20A "Safebox-A"

Acoustic Safe ASU-20A "Safebox-A"


Acoustic ultrasonic safe ASU-20A with an automatic switch is designed to protect speech and any other acoustic information from leakage through smartphones, tablets and headsets. Protects up to 20 phones simultaneously.

Acoustic Safe DIY Kit ASU-20-DIY

Acoustic Safe DIY Kit ASU-20-DIY


DIY kit ASU-20-DIY The ASU-20-DIY kit allows to make an acoustic safe from almost any box, suitcase or interior item of suitable size.

12 Volt Car Power Adapter ASU-PA12

12 Volt Car Power Adapter ASU-PA12


12 Volt car power adapter to use acoustic safes in a car.

Assembled and configured ASU-20-PCB boards for local production of acoustic safes

Assembled and configured ASU-20-PCB boards for local production of acoustic safes

$ ask

Assembled ASU-20-PCB boards and, if necessary, other parts for organizing local production of acoustic safes.

Payment and Delivery

You can pay for acoustic safes by invoice from our Thai company. Delivery is carried out by various international carriers. Please check with us for terms and conditions. 

Wholesale Buyers and Distributors 

Discounts are provided to wholesale buyers and distributors.  


Acoustic safes are useful not only in offices, but also in places of rest, where sometimes the most important negotiations take place. The video demonstrates the complete suppression of the microphone of a smartphone inside the acoustic safe.

Phone / Telegram

+66 823 48 48 99 / @spycase


159/117 Moo 5, T. Si Sunthon, A. Thalang, Phuket, Thailand 83110 POCKETELECTRIC CO.,LTD

Business Hours

9:00 - 21:00 (GMT+7) Mon - Sun