My Strange Little Corner of the Web...

My growing collection of unusual noises...

I created this page to help my friends with scanners & ham radios identify the growing number of new & unusual sounds they might hear when monitoring outside the amateur bands.

I'm always looking for new additions to this page - if you have high-quality audio recordings that you want added to the database here, contact me. Do not e-mail me with questions like 'what is this sound'? - if it does not remotely sound similar to anything I have posted here, I won't know either!

All sounds are in MP3 format. Click on the title of each to play them. These sounds are public domain, and may be used by anyone. If you plan to use these for commercial purposes, please have the courtesy to give me credit as the source.

Section 1 - Unit Identifiers

Motorola MDC-1200 - This is the most common form of unit ID found in public safety. This is either broadcast at the start or the end of a unit's transmission (or both, if you so choose to have it programmed that way). The user's radio can also be programmed to emit a tone on key-up (to remind the user to wait before speaking, as the unit's mic is not activated until the ID is sent).

MDC-1200 Preamble - This added feature of the MDC signaling system is designed to allow a properly programmed radio to mute the ID signal part of the transmission. The raw burst of data tells the radio to mute the speaker audio for a pre-determined length of time (usually 400 or 500 ms). If the radio is programmed correctly, the end-user (or dispatcher) would not hear this sound at all, only the person's voice.

MDC-1200 Echo - This sound is most commonly heard in a police cruiser or ambulance cab. What you are hearing is the very end of the 'wait tone' echoing off the inside of the vehicle and being picked up by the mic. Also, there are several Motorola radios that emit an "ok" beep, just like a key press, when the PTT is used. Certain models of the Maxtrac's and 'Pro' series radios were famous for this.

Motorola MDC-600 - This is an alternate form of the same protocol used in MDC-1200, but at only 600 baud. The FDNY was a primary user of this format before their recent radio system upgrades. (Thanks Matt!)

Motorola ATIS - ATIS stands for Automatic Transmitter Identification System. It is predominantly used by marine vessels on inland waterways throughout Europe. This was a signaling format available in the U.S. on the HT1000 & VISAR, along with MDC & STAR. It is based on the DSC protocol. (Thanks Greg!)

MODAT - This is an older form of unit ID by Motorola. This is actually a slower-speed data transmission rate than MDC-1200, and what makes it truly unique is that the actual sound of the ID varies when you change the ID code. Baltimore FD and LAPD used to use this form of ID before they both went to digital trunking. MONOC EMS in Monmouth & Ocean Counties (NJ) use this currently.

GE STAR - This form of unit ID was General Electric's answer to MDC-1200 when they where still involved in the 2-way business (before selling that division to Ericsson).

GE G-Star 400 - I recorded this while monitoring Voorhees PD in Camden County, NJ. Only about half of the patrol units on a shift had this at the end of their transmissions.

DTMF - This is a simple stream of usually 4 or more DTMF tones used to ID the radio that is transmitting. (Thanks Greg!)

Kenwood FleetSync - FleetSync is a digital messaging & identification protocol developed by Kenwood that is used in their line of radios. It it quite similar to Motorola's MDC, but has many more capabilities. This second sample is an example of what it would sound like if the feature would be used to send a unit-to-unit message, GPS location burst, etc... (Thanks to Rich, N2DLX)

  • Here is an updated sample of FleetSync in the more common 1200-buad mode. (Thanks Augy!)
  • Here is a sample in the lesser-used 2400-baud mode. (Thanks Augy!)

Tait MP7 - MP7 is the digital identification protocol used on MPT1327 trunking systems. (Thanks Adam!)

Section 2 - Voice Scrambling & Encryption

Motorola DVP-XL - This recording is from the Gloucester Twp. PD in Camden County, NJ. The dispatcher usually transmits a short warning tone & then calls the units she needs to speak to in 'secure' mode. As you can hear, the units in the field respond back to dispatch 'in the clear'. Gloucester Twp. uses this only as needed, and I've never heard any department use this full-time.

Motorola DES-XL - This is another format of analog encryption designed by Motorola that was designed to have greater range that standard DES before the signal becomes unintelligible. As with all analog encryption formats, the recovered audio is less than desirable. (Thanks Nick!)

AES & DES Encryption - This is the most wide-spread use of encryption on public-safety radio systems at this time.. This is almost never used on analog systems, because it has a detrimental effect on the quality of the decoded audio. Most first-generation Uniden digital scanners do not block the audio playback of encrypted signals, and I was able to get a very clean copy from my BC-796D before I sold it. This recording is from the Franklin Twp. trunk system here in NJ. If you were to stumble across this with an analog receiver, it would sound identical to the ASTRO sample in the next section. The primary difference between AES & DES is the cipher strength: DES is 64-bit and AES is 256-bit.

AES Encryption on ProVoice - This recording is of AES encryption being used on the Middlesex County, NJ EDACS system (Thanks Greg!)

Encryption on Aegis - This is a sample of encryption being used on Aegis digital voice. Here is what it sounds like decoded by a proper receiving radio. (Thanks Greg!)

Aegis VGE Encryption - This is a proprietary 64-bit encryption used on older GE radios (Thanks Ray!) new

Unknown Analog Encryption - This recording is from a conventional UHF channel that is shared between Woodbridge & Perth Amboy PD's. If anyone can help identify what this is, it would be greatly appreciated! (Thanks Greg!)

Kenwood NEXEDGE Digital Encryption (Thanks Nick!)

MotoTRBO Enhanced Privacy Digital Encryption - This is what it sounds like in the raw (Thanks Nick & Ray!) update

DMR Enhanced Privacy - This is the 128-bit encryption featured on the new Tytera MD-380 portable radio (Thanks Ray!) new

Marconi DM8000 DES

MASC Voice Scrambling

Transcrypt International 410 Voice Scrambling

Transcrypt International 430 Voice Scrambling

Transcrypt International 460 Voice Scrambling

Transcrypt International 460 Voice Scrambling (Properly Decoded)

FFT-Style Voice Scrambling

Midian TVS-2 Voice Scrambling (standard single-hop)

Midian TVS-2 Voice Scrambling (high security double-hop)

Selectone ST-25 Rolling Code Sweeping Scrambler

Split-Band Voice Scrambling

MX COM Variable Split Band (VSB) Scrambling

Static Voice Inversion

Italian Police Analog Voice Scrambling

Rolling Code Speech Frequency Inversion

Icom UT-98 Marine Radio Voice Scrambler

Icom UT-109 LMR Voice Scrambler

Section 3 - Digital Voice Formats

Motorola ASTRO VSELP - This was Motorola's first digital voice solution marketed under the ASTRO name. This was a in-house modification to the Vector Sum Excited Linear Predictive standard that was used in the first TDMA cell phones. Motorola also modified this into the IDEN format that is used by NEXTEL phones (see below). Very few jurisdictions use this type of system anymore (Trenton, NJ & Cleveland, OH). This is not a Project 25-compliant system, and cannot be picked up on any known scanner. Here is a sample of decoded audio. These two new samples are of VSELP being used on simplex, and simplex with DES-XL encryption. (Thanks Greg & Nick!)

Motorola ASTRO IMBE - This is Motorola's current ASTRO voice format offering. This type of emission is known as C4FM, and the technology in use is the IMBE (Improved Multi-Band Excitation) vocoder from Digital Voice Systems Inc. This is a much better sample of decoded audio from the Bucks County, PA 500 MHz trunk system. There are almost half a dozen manufacturers that produce radios that are capable of 'Conventional P25 Operation' now, so this signal format is no longer exclusive to Motorola. (Thanks Nick!)

P25 H-DQPSK - This is what the repeaters on a Phase-II (TDMA) trunk system transmit on the voice channels when a conversation is in progress. (Thanks Augy!)

Harris ProVoice - This is the current form of digital voice originally developed by Ericsson. This is also an IMBE signal style, but is not Project 25 compliant (whereas Motorola's is). This decoded voice clip is an updated sample from the Middlesex County EDACS system There is currently no scanner or receiver that can decode this. Here is an alternate sample that shows the slight change in the raw audio when the signal is encrypted. (Thanks Greg!)

Harris Aegis - This was the first-generation digital voice solution from GE. This format is not well liked because the decoded voice leaves much to be desired. It is not Project 25 compliant, nor can it inter-mix with ProVoice. As with ProVoice, there is no scanner or receiver that can decode this. Here is a sample of the decoded audio. (Thanks Greg!)

ICOM D-STAR - This is the new digital audio format in use by the D-STAR amateur radio system. This is what you would hear if you came across a D-STAR repeater with a regular analog amateur radio. This is an AMBE vocoder that uses the GMSK modulation style (similar to the world-wide GSM cell phone standard).

ICOM D-STAR vs. FM - This is KC5ZRQ testing the outer range limits of D-STAR vs. analog FM on simplex. This is a pretty impressive example of how D-STAR will hold it's 'intelligibility', while the FM capture degraded to a pretty bad level.

NXDN - The is a brand-new digital format being co-designed by Kenwood & ICOM that is geared towards the business sector. It is designed for those that want to meet the up-coming FCC mandate for 6.25KHz channel spacing, but that can't (or don't) want to move to the APCO P25 Phase-II equipment that will soon come to market. The format is based on the AMBE+2 vocoder (similar to ICOM's D-STAR), but uses a 4-level FSK waveform (FDMA). The radios are capable of narrowband analog, along with 12.5 KHz & 6.25 KHz digital emissions. Kenwood is offering the system under the name NEXEDGEâ„¢, and the radios are capable of both conventional & trunking operation. The attached sound file contains all of the formats the system is capable of producing, including the raw data streams of both digital formats. (Thanks Rich! - Audio is credited to David Sterrett, N1DAS)

DMR - DMR stands for Digital Mobile Radio, and it is an open standard created by the ETSI for professional mobile radio users worldwide. Motorola brought this technology to market in the US as MotoTRBO, but there numerous radio manufacturers producing equipment now. It is based on a 2:1 TDMA format that uses the AMBE+2 vocoder & a 4-level FSK waveform. There is now a substantial presence in amateur radio of this format. This is what the signal sounds like when used in TDMA mode through a repeater, and FDMA mode when used simplex (talk-around) mode. (Thanks to the N6DVA group, Jerry, & Nick for the audio!)

Motorola DTR - This is a digital format used by Motorola DTR-series personal/jobsite portable radios. It utilizes frequency-hopping spread-spectrum signal technology (VSELP audio at 11 hops per second) on the 900MHz band. It is near impossible to get a copy of the raw audio without a service monitor due to the FHSS signal. The Nextel off-network 'DirectTalk' technology is based off of this same design, but the two formats are not compatible. (Thanks Greg & Ray!)

Yaesu C4FM - This is the version of digital modulation Yaesu chose for their new 'System Fusion' amateur radios. This is an FDMA signal format using the AMBE+ codec & is not compatible with C4FM P25 radios. Here is a sample of the decoded audio. (Thanks Greg & Bob!)

dPMR - dPMR is another open-standard digital format created by the ETSI, and is very similar to NXDN. It is used almost exclusively in the 6.25KHz mode, and two separate signal streams can occupy the same 12.5KHz space without any interference to each other. (Thanks Petardete!)

Section 4 - Trunked Radio Systems

First-Generation Motorola Control Channel - The title is pretty self-explanatory - This was the 3600 baud data stream used in the first Type-I trunk systems.

Current Motorola Control Channel (SmartNet) - This is the current control channel style in use for most modern Motorola Type-I, Type-II, and Type-IIi Hybrid systems. This is a 3600 baud data stream, and was sampled from the East Brunswick, NJ SmartNet system.

Current Motorola Control Channel (SmartZone) - This control channel stream is very similar to the SmartNet stream above, but was recorded from the NJ State Police Troop B SmartZone system. I'm unsure if the difference in the sound is because the system is a SmartZone, or because of the much larger volume of data being transmitted.

Motorola SmartZone OmniLink Control Channel - In the last few months of 2006, the NJSP completed an upgrade to the statewide trunked radio system. They upgraded the 3 separate SmartZone system in to one seamless OmniLink setup. Users from any part of the state can now leave their radios turned to their primary home talkgroup, and the system will follow them, even if they cross system boundaries. The upgrade seems to have added some interesting characteristics to the sound of the data stream.

APCO Project-25 Control Channel - Project-25 trunking is a completely digital, vendor-independent  specification that was initially developed by Motorola, and now has product offerings & support from Harris, Kenwood, EF Johnson, & others. The original Phase-I systems are deployed as C4FM or CQPSK-LSM (Compatible Quadrature Phase Shift Keying - Linear Simulcast Modulation) if sent at a 12.5 KHz spread. If the system is set at the new 6.25 KHz spacing, it is just known as CQPSK. This is a 9600 baud data stream, and is what a Motorola-built Phase-I (C4FM) system sounds like.

P25 Test Patterns - These are a pair of data streams submitted by the same user as the sounds above. Neither was able to be decoded as a control or voice transmission. Any help in identifying what these are is greatly appreciated! - 700MHz test transmission - 800MHz test transmission.

Motorola Trunking Failsoft Tone - This is a sample of the sound that a Motorola trunk system will make if the site controller has failed, and the channels are operating in a conventional mode. The static you hear between the tones is encrypted analog voice. Here is an updated sample of a Type-II SmartNet system when operating in this condition. (Thanks Greg & Matt!)

Harris EDACS Wideband Control Channel - This is the most common form of control channel used in EDACS systems. This is a 9600 baud data stream. When the system is passing voice traffic, you can actually hear the rhythm of the data change.

Harris EDACS Narrowband Control Channel - This is a very seldom seen variant of the standard EDACS system. Here in NJ, Verona Twp. on UHF and Trump Plaza Casino on 900 MHz use this system. This is a 4800 baud data stream.

EDACS Scan-Defeat Tone - The actual name for this sound is 'Scrambled Data Calls', and was a system diagnostic tool to verify on a regular basis that the working channel repeater was passing random data correctly. It was originally designed as an automated test using something other than normal system data. Once system admins discovered local media outlets complaining about the noise, many used this as an excuse to enable the feature at much more frequent intervals as a deterrent to outside listeners.  (Thanks Jim & Mark!)

EDACS 'Jingle' - This sound was implemented by GE as a way for engineers & techs to be able to confirm the 'Channel Drop Message' had been properly sent by the radios in the system when monitoring on a standard analog receiver. Actual EDACS radios receive the CDM digitally & don't rely on the sound that's heard over the air. (Thanks Greg & Mark!)

Harris OpenSky - This is the latest technology system to come out of Harris. This system is basically a wide-area 'computer network'. Every radio has an IP address, and the mobiles can fully support voice & data simultaneously (i.e. - an officer's MDT). This system utilizes the AMBE vocoder (similar to the ICOM D-STAR system), and transmits over a 4:1 TDMA broadcast format. The fundamental design of this system is completely different compared to a Motorola or EDACS system - They use their control channel to tell units on the system to switch to different voice frequencies for reception of radio traffic. OpenSky sends the voice component back over the same stream that carries the control data. This sample came from the Pennsylvania state-wide system. There is currently no form of receiver that can decode this system. Thanks to an anonymous user, we now have an audio clip of what the format sounds like to the end-user (via a Harris M7200 mobile radio)!

LTR Passport Data Stream - This is an unknown data stream copied off the NJ Turnpike Authority 220 MHz Passport system. If anyone knows what is being sent in these (possibly GPS location data?), please let me know. (Thanks Greg!)

MotoTRBO ConnectPlus Control Channel - Sounding somewhat similar to a Motorola Type-II 3600-baud control channel, the tempo of the control channel actually changes as users are talking on the voice channels. (Thanks Nick!)

MotoTRBO CapacityPlus 'Resting Burst' - MotoTRBO CapacityPlus trunking systems broadcast this every 2 seconds to keep subscriber radios updated & synced to the system. (Thanks Nick!)

Kenwood NEXEDGE Narrowband Control Channel - This is the control channel used by Kenwood's version of NXDN in the 4800 baud (6.25k) trunking format. This trunking mode is incompatible with the Icom IDAS NXDN radios (they have their own version of trunking called MULTITRUNK). (Thanks Nick!)

Kenwood NEXEDGE Wideband Control Channel - This is the control channel used by Kenwood NEXEDGE NXDN trunking when operating in the 9600 baud (12.5k) format. (Thanks Jacob!)

TETRA - This is a highly successful trunking radio network design used outside the USA in many European, Asian, & South American countries. It is a 4:1 TDMA system that is primarily deployed at 380MHz and above. A well-written description of the system can be found here, and an audio sample is now available of what it sounds like to the end-user (DMO mode - non-repeated). The NJ Transit corporation has won approval to deploy a TETRA system here in the U.S. to replace its aging Motorola Type-IIi trunk system using their existing 800MHz licenses. The infrastructure is now on-air, and data stream sounds noticeably different then the European version. (Thanks Roland & Greg!)

TETRAPOL - This is the second most popular trunking format in Europe for those that choose not to deploy TETRA systems. These systems are primarily used by police or military organizations. It is a narrowband format FDMA signal using GMSK modulation. The systems employ strong end-to-end encryption be default, and cannot be monitored by scanners or receivers. This is a sample of the voice signal 'in the raw'. (Thanks Martin!)

MPT-1327 - This is a trunking protocol that is very popular in the UK. There are very few systems here in US that use this (Decatur, TX and Douglas County, WA). There is currently no form of receiver that can decode this system.

Motorola iDEN - I figured I'd add this here because the iDEN networks used by NEXTEL, Telus, SouthernLinc, etc. are a derivative of Motorola's older VSELP digital trunking transmitted over a standard 6:1 TDMA cell format. This is what it sounds like in the raw.

Motorola SpectraTac Receiver - The NJSP system used to use this model of receiver with a 'voting' comparator to mange incoming signals from the multiple receive sites connected to the controller. Since the remote links are never turned off, and always transmitting, they send a 2175 Hz. tone when not broadcasting audio. What you are hearing here is the split-second delay between the Trooper ending his transmission, and the comparator realizing that it needs to switch off broadcasting that receiver. (Thanks Steve!)

Motorola Talk Permit Tone - This is the sound a user's radio makes when the request to transmit on a trunk system has been granted by the site controller. (Thanks Matt!)

Harris Carrier Control Timer - This is the sound that a modern Harris radio will make when you are about to reach the TX timeout threshold. (Thanks Fernando!)