"BugHunter DAudio BDA-4 Voices" is a new microphone, dictaphone jammer with 8 ultrasonic transducers and 1 acoustic speaker. The newly upgraded jamming system creates acoustic interference in the air thus allowing to suppress even highly protected microphones (IP65-68). Joint use of 8 ultrasonic transducers located on the front panel and 1 acoustic speaker creates a "veil" with ultrasonic and acoustic interference — 2 in 1.
If used properly, BDA-4 is capable of jamming most types of microphones, including professional ones, within a range from 60 cm to 9 m (2 ft to 30 ft) depending on the microphone’s protection level. We recommend to use the device in square rooms with a height of up to 3.5 m (11 ft) for maximum efficiency. Ultrasonic interference will be reflected multiple times thus enhancing the power of jamming.
Подавитель микрофонов, подслушивающих устройств и диктофонов"BugHunter DAudio bda-4 Voices" 
The device is supplied with a remote control which allows to turn the jammer on and off at a distance of up to 10 m (33 ft). BDA-4 is a stationary device powered only by 110/220V mains which ensures the maximum power of jamming interference.
Подавитель микрофонов, подслушивающих устройств и диктофонов"BugHunter DAudio bda-4 Voices" 
"BugHunter DAudio BDA-4 Voices" features a new jamming system:
Ultrasound combined with audible frequency. Now ultrasonic interference consists of two frequencies simultaneously: ultrasound (frequency range is over 20 kHz) and acoustic sound (frequency range is 18-19 kHz) with speech-like noise that not only jams microphones, but overloads them. Dictaphones can’t record sounds and only receive interference transmitted from BDA-4. The interference signal forms not immediately, but in the air, approximately 40-60 cm (1.3-2.0 ft) from the transducers, when the frequencies overlap each other, forming a dense and powerful interference.
This video demonstrates test recordings on iPhone 11 Pro, Huawei P20 Pro, iPad Air 2 with "BugHunter DAudio BDA-4 Voices" operating
White noise mode. It is an indispensable mode for negotiations when all parties are aware of the jammer operating. This mode provides 100% protection from eavesdropping. BDA-4 mixes your words with the noise signal that comes out of its transducers and covers a fairly large frequency range with numerous reflections in a room, which causes a "shock" to any dictaphone.
Подавитель микрофонов, подслушивающих устройств и диктофонов"BugHunter DAudio bda-4 Voices" 
BDA-4 is designed to protect negotiations from eavesdropping devices. The device is capable of jamming radio microphones, wired microphones and most types of professional digital dictaphones, including dictaphones built into smartphones.
Our jammer is completely safe for people as it generates frequencies that are not perceived by human ears. The only thing which is heard clearly is "white noise". "White noise" is a combination of sounds with a slight pressure in comparison to ultrasonic interference. Ultrasonic interference reaches record sound pressure of 125 dB. *
* Ultrasound pressure level may exceed safe levels in the distance of 1 m (3 ft) and less from the operating device. This may cause unwellness.
Подавитель микрофонов, подслушивающих устройств и диктофонов"BugHunter DAudio bda-4 Voices" 
Operating principle
The device generates ultrasonic signal through 8 transducers and 1 additional speaker with the frequency range of 18-19 kHz. Frequency of ultrasound is determined by a micro-controller and variates according to a specially developed algorithm. A combined ultrasonic signal generated by the device affects eavesdropping devices (microphones, dictaphones, cellphones etc.), making them overloaded on the wide frequency range. Eavesdropping devices do not break down, but either chaotically record only indiscriminate noise in which conversation can't be distinguished or just stop recording.
Подавитель микрофонов, подслушивающих устройств и диктофонов"BugHunter DAudio bda-4 Voices" 
Besides, powerful speaker creates acoustic speech-like interference which destroys the meaning of the conversation. As a result, spyware record only indiscriminate muttering and restoring the conversation becomes physically impossible. Acoustic interference is generated randomly so it can't be filtered out even by special equipment.
Testing BugHunter BDA-4 on different types of voice recording devices
Such a complex security system provides maximum protection and confidentiality. Even the most expensive spyware and eavesdropping devices turn into useless "toys" as they simply can’t record any information. They only receive indiscriminate noise which is completely impossible to be unscrambled. At the same time, generated interference does not disrupt conversation as ultrasonic signals are not perceived by human ear and the volume of speech-like noise can be easily adjusted. You will hear your interlocutor whereas nobody will be able to eavesdrop on you!
Подавитель микрофонов, подслушивающих устройств и диктофонов"BugHunter DAudio bda-4 Voices" 
Flexible volume adjustment
Acoustic speech-like interference guarantees confidentiality of your conversations, but has one flaw: unlike ultrasound it can be heard and may become a nuisance during negotiations. Our developers took this into account and developed "BugHunter DAudio BDA-4 Voices" with an ability to adjust the volume of the acoustic interference. You can always adjust the volume so that device won't muffle your speech and you could speak comfortably. If the jammer is a nuisance, just turn the volume down by turning a knob located on the back of the device’s housing to a minimum. This way you will turn the acoustic interference off. Turn it back on if you want to volume it up and get better protection.
Подавитель микрофонов, подслушивающих устройств и диктофонов"BugHunter DAudio bda-4 Voices" 
Without acoustic interference the device operates in the combined ultrasound mode in which it can hardly be heard, especially with an air conditioner or music turned on. You can chat without paying attention to the device operating. Moreover, it looks like a computer speaker and you can use it inconspicuously, if you don’t want to demonstrate that you protect your conversations.
However, it is important to bear in mind that the protection level decreases if you don’t use the acoustic interference. If you need to jam ALL possible microphones providing 100% confidentiality, you have to reconcile with the slight noise generated by the device. On the other hand, you will be assured that no one is spying on you.
Using the jammer
Anybody, even a non-professional can use the jammer. All you need to do is point the transducers in a direction of an expected location of recording devices and turn it on via the remote control. You can make your protection more reliable by activating the speech-like interference using a rotary knob on the back of the device’s housing.
It is important to realize that jamming is more effective in small rooms because of numerous reflections of the waves (interference). If you use only one device, it is recommended to stand behind it. If there are several devices operating and the room’s height does not exceed 3.5 m (11 ft), you may stand anywhere. Ultrasound spreads with maximum efficiency only within 10 m (33 ft). Consider this if your room is wider and make sure you are protected sufficiently by using several devices or via joint use of BDA-4 and BDA-3 jammer.
Technical features:
Dimensions
180 х 165 х 110 mm (7.0 x 6.5 x 4.3 in)
Weight
2 kg (4.4 lb)
Power
110/220 V network
Power consumption
No more than 0.7 A
Sound pressure level at 1 m (3.3 ft) distance from the device
Not less than 125 dB
Range
optimal — up to 2 m (7 ft)
maximal — up to 7 m (23 ft)
Jamming method
Ultrasonic interference + acoustic interference at 18-19 kHz frequency + acoustic speech-like interference
Remote control action range
up to 10 m (33 f