Audio Surveillance Equipment for Investigators

Audio Amplifiers
Image by Pete Linforth from Pixabay

Overview of Audio Surveillance Tools

Audio surveillance equipment is used by intelligence agencies, law enforcement, and private investigators to monitor and record subjects in various settings. Audio surveillance can be conducted from a distance using covert listening devices hidden inside the dwelling. Or, audio amplifiers can be attached to a person inside the house (such as an informant). Also, audio amplifiers can be used to amplify sounds from a distance.

This article will review audio amplification systems and digital audio recording devices. In addition, I’ll suggest where you can purchase the equipment at and the Home Security Superstore.

Audio Amplifier Systems

Audio amplifiers are electronic devices that amplify low-power audio signals (primarily composed of frequencies between 20 – 20 000 Hz, the human hearing range) to a higher level. The amplification equipment can be used indoors or outdoors to listen to sounds and conversations at a distance.

Audio amplification equipment helps private investigators and police officers to hear conversations that are taking place in a nearby location, such as in another room or on the other side of the park.

This lets private investigators listen to what is being said without the other party’s knowledge. The basic point is to hear what is being discussed while remaining unseen. Also, investigators use audio amplification systems for many other purposes. For example, eavesdropping on conversations from a distance. Or to check in on a witness.

Targeted Amplification

The amplification devices can be targeted by pointing the unit toward the sounds you want to hear. The target could be a person conversing with someone else, someone talking on the phone, or multiple individuals having a group discussion. The sounds that are targeted are then amplified as much as ten times.

What’s Included

The typical equipment with the sound amplification tool includes the listening device, the “sound catching” cone, a microphone, mounting clips, batteries, carrying, and storage cases. In addition, some packages include an audio out jack and cables to record conversations. Also, many packages include noise reduction and wind reduction capabilities to help filter out unwanted background noise. This can be helpful when playing back the recording.

Other Uses for Sound Amplification Equipment

In addition to surveillance, audio amplifiers can be used for nature observation, concerts, hunting, bird watching, lectures, personal security, sporting events, or watching TV. The listening distance will vary depending on the particular device you are using, but count on being able to pick up conversations from over 300 yards away.

As a protection mechanism, some audio amplifiers come equipped with auto-shutoff in case the sound becomes too loud.

Digital Voice Audio Recorders

A digital audio voice recorder is a compact and versatile device designed for capturing high-quality audio recordings in a variety of settings. Utilizing digital technology, these recorders offer significant advantages over traditional analog counterparts. They typically feature built-in microphones or external microphone inputs, enabling users to record clear and crisp sound in meetings, interviews, lectures, and other scenarios.

One of the key benefits of digital audio voice recorders is their ability to store recordings in digital formats such as MP3 or WAV, facilitating easy playback and sharing across different devices. Many models come equipped with ample storage capacity or expandable memory options, ensuring users can capture lengthy recordings without concerns about running out of space.

User-friendly interfaces and intuitive controls make these devices accessible to individuals of all technical levels. Some advanced models may include additional features like noise reduction, voice activation, and customizable settings to enhance recording quality. USB connectivity simplifies file transfers to computers for editing or storage.

Digital audio voice recorders have become essential tools for professionals, students, journalists, and anyone requiring a portable, reliable solution for capturing and preserving audio content. Their compact size, ease of use, and advanced features contribute to their popularity in various personal and professional applications.

Private Investigator Use

Private investigators use digital audio voice recorders to record case notes, record witness interviews, and capture voices and sounds as needed during a surveillance mission.

When working as a private eye, you don’t always have the time to stop and write everything down. In old movies and TV shows, P.I.’s often pulled out a handheld flip pad to jot down a few notes or facts when working on a case. However, modern detectives are always on the go, and their hands aren’t always free for writing. For example, you may be on a long surveillance mission. Your hands may be busy working with audio equipment, taking pictures with cameras, or driving a vehicle to follow a subject.

A voice recording device will help you capture important notes and set reminders without missing a step while keeping your hands free to perform other tasks. Then, when you return to your office, replay the notes and transcribe what is meaningful to your PC, tablet, or phone.

Voice recorders are great when you don’t have a pen and need to record important information. Use a recorder to capture ideas and thoughts on your case, record surveillance notes, or set important reminders.

Many of the latest models offer high-quality sound, slim designs for easy storage and concealment, one-touch recording, and plenty of storage space to keep hours of data. Additional equipment for connecting to a computer or mobile device is often included.

Sony Digital Voice Recorder

Sony ICD-PX370 Mono Digital Voice Recorder with Built-In USB Voice Recorder,black
  • Record MP3 Audio quickly and easily
  • Up to 57 hours of battery life for extended recording (MP3 128Kbps stereo)
  • Built in, direct USB Connection for quick file transfer to your PC

I recommend a digital voice recorder for every private investigator, especially those conducting surveillance and interviewing witnesses.

The recording device has an amazing 57 hours of battery life, so you can spend more time using the recording and charging less. In addition, it comes with a handy built-in direct USB connection at the bottom to allow you to quickly and easily transfer audio files to your computer or tablet.  You can use it to record witness statements, interview conversations, and record your case notes. Also, it is small enough to fit secretly in your pocket to record conversations covertly.

Important Note: Check your state and local laws about recording witnesses or other spoken statements. It is illegal in most states to record a person’s voice without their consent.

Please note that these tools are not specifically designed to intercept oral communication surreptitiously. Use for this purpose seriously violates federal laws. Check your state and local laws before purchasing such equipment, and be aware of those laws when using the tools.

The information in this article is not intended to condone any unauthorized use of audio amplifiers, such as illegal tapping into other people’s phone conversations. It is the purchaser’s responsibility to comply with all Federal and state privacy rules & regulations.


Please comment below if you have questions about audio amplifiers and sound surveillance equipment. Or, learn about other types of spy gear and equipment.

Related: How to find hidden surveillance bugs.

Michael Kissiah is the owner of Brandy Lane Publishing, LLC, which owns and operates a small portfolio of websites, including Michael created more than 20 years ago after working as a private investigator in the state of Florida. Since that time, he has become an expert at how to find information online and has written over 1000 articles on topics related to the investigation industry. In addition, he is the author of the "Private Investigator Licensing Handbook", available at



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