Every hobby is full of three-letter acronyms that are entirely incomprehensible to anyone outside of the community. All too often, beginners to personal audio get overwhelmed by the alphabet soup of naming conventions. Even veterans skimming through a review or technical article can sometimes use an easy point of reference.
To help, we present this quick reference guide that includes most of the common headphone acronyms that you are likely to encounter on your audio journey.
| Acronym | Definition | Description |
|---|---|---|
| AAC | Advanced Audio Coding | An audio coding standard for lossy digital audio compression. Wireless CODEC of choice for Apple. |
| A/D | Analog to Digital | The conversion process from analog audio to a digital file. |
| ADC | Analog to Digital Converter or Audio Device Class (when referring to USB audio. | USB peripherals that support the Audio Device Class send or receive audio and additional functionality. |
| AES3 | Audio Engineering Society | A standard created by the Audio Engineering Society for transferring a stereo digital audio signal (2 channels of uncompressed PCM audio) over a single XLR digital cable. S/PDIF is a variant. |
| AIFF | Audio Interchange File Format | An uncompressed file format developed by Apple in 1988 as a WAV alternative. |
| ALAC | Apple Lossless Audio CODEC | An open-source format created by Apple and competing with FLAC. |
| aptX | Audio Processing Technology | A family of proprietary audio codec compression algorithms owned by Qualcomm, with a heavy emphasis on wireless audio applications. |
| ASIO | Audio Stream Input/Output | A driver protocol for digital audio, providing a low-latency and a high fidelity interface. |
| ATRAC | Adaptive Transform Acoustic Coding | A family of proprietary audio compression algorithms developed by Sony. MiniDisc was the first commercial product to incorporate ATRAC in 1992. |
| BA | Balanced Armature | Small and lightweight driver originally developed for hearing aids, featuring a vibrating reed suspended in a magnetic field within an enclosure. Often combined with multiple variations in an IEM. |
| BNC | Bayonet Neill–Concelman | A miniature quick connect/disconnect connector used for coaxial cable. |
| CBR | Constant Bit Rate | A method for encoding audio files that keeps the bitrate unchanging. |
| CD | Compact Disc | Co-developed by Philips and Sony and released in 1982. |
| CIEM | Custom In-Ear Monitor | A type of IEM that is made specifically to fit a single person’s ear canal. |
| COAX | Coaxial | A standard electrical connection of the S/PDIF standard, typically through a single 75 ohm coaxial (2-conductor) cable. |
| CODEC | Coder-Decoder | A device or computer program which encodes or decodes a digital data stream or signal. |
| D/A | Digital to Analog | The conversion process from a digital file to analog audio. |
| DAC | Digital to Analog Converter | A device that decodes digital files to analog. Maybe abbreviated as ‘D/A’, ‘D2A’, or ‘D-to-A’. |
| DAP | Digital Audio Player | An electronic device capable of storing and playing high-resolution music or media files. |
| DAT | Digital Audio Tape | Analog signal recording and playback medium developed by Sony and introduced in 1987. |
| DD | Dynamic Driver | Traditional speaker driver type featuring a diaphragm moved by a coil suspended in a magnetic field. |
| DOP | DSD Over PCM | An open standard method for transferring DSD audio over PCM. |
| DSD | Direct Stream Digital | Sony and Philips designed a system of digitally recreating audible signals for the Super Audio CD (SACD). |
| DTS | Digital Theater Systems | Surround sound formats for both commercial/theatrical and consumer (home theatre) applications. |
| EAC | Enhanced Audio CODEC | An audio codec developed and owned by Beijing E-World, to compress the audio signal by utilizing the redundancy as well as the relevancy. |
| FLAC | Free Lossless Audio CODEC | The (almost) universal standard, open-source format for lossless digital music files. |
| FPGA | Field Programmable Gate Array | A general-use powerful computing chip that can be programmed for any number of purposes. Used by Chord Electronics (amongst others) for their DAC products. |
| HD | High-Definition | Typically applied to video content, but may refer to Hi-Res Audio. |
| HDMI | High-Definition Multimedia Interface | A proprietary audio/video interface for transmitting uncompressed video data and compressed or uncompressed digital audio data. |
| Hi-Fi | High Fidelity | The high-quality reproduction of sound. |
| Hi-Res Audio | High-Resolution Audio | Digital music files that have a higher sampling frequency and/or bit depth than CD – which is specified at 16bit/44.1kHz. |
| IEM | In-Ear Monitor | Originally intended for live musicians, now a popular type of headphone that inserts into the ear canal. |
| IMD | Intermodulation Distortion | The ratio (in dB) between the power of fundamental tones and third-order distortion products. |
| IPX | Ingress Protection Code | The level of protection of a device against water ingress (waterproofness or water-resistance). The IPX mark is followed by a number 0-8 (0 – no protection at all, 8 – fully submersible in fresh water of up to 3m/9ft depth). Not rated for saltwater. |
| LAN | Local Area Network | A computer network that interconnects devices within a limited area. |
| LDAC | Low latency Digital Audio Codec | Developed by Sony, lossy but supports up to 24-bit/96kHz and is the first wireless codec with the ‘Hi-Res Audio Wireless’ certification. |
| LHDC | Low latency High-Definition CODEC | Higher quality CODEC that allows almost 3 times the data transmitted wirelessly compared to SBC. |
| LED | Light Emitting Diode | Typically used as an indicator for power etc. |
| MP3 | MPEG-1 Audio Layer III or MPEG-2 Audio Layer III | Audio coding standard for lossy digital audio compression. |
| M4A | MPEG-4 | A format encoded with either AAC or ALAC (and as such can be lossy or lossless. |
| MMCX | Micro-Miniature Coaxial | Very small coaxial connectors, with a lock-snap mechanism allowing 360-degree rotation often used on IEMs in place of a 2-pin connector. |
| MQA | Master Quality Authenticated | Launched in 2014 by Meridian Audio and is a hybrid of lossy and lossless compression. |
| NFC | Near Field Communication | An automatic method of wireless data transfer used to quickly pair Bluetooth devices and for tap and go payments from devices. |
| NRR | Noise Reduction Rating | The standard for hearing protection attenuation across North America. Single Number Rating (SNR) is the EU’s standard. |
| OCC | Ohno Continuous Cast | A casting process for copper or silver wire that draws a single crystal up to 125 meters in length, providing the least possible oxides and other impurities. |
| OFC | Oxygen-Free Copper | Copper alloys that have been refined to reduce the level of oxygen contained to .001% or below. |
| OGG | Ogg Vorbis | Somewhat uncommon free lossy digital audio file format. |
| Opamp | Operational Amplifier | A DC-coupled, high-gain electronic voltage amplifier chip with a differential input and (usually) a single-ended output. |
| OTA | Over The Air | A synonym for wireless, typically referring for a method of updating software, such as firmware, achieved without connecting a device with cables. |
| OTG | USB On The Go | Allows USB devices (such as tablets or smartphones) to act as a host, allowing other USB devices, such as DACs, to be attached to them. |
| OTL | Output Transformerless | A type of vacuum tube audio power amplifier which omits an output transformer for greater linearity and fidelity. Common examples are the Bottlehead Crack and the Darkvoice 336SE. |
| PCM | Pulse-Code Modulation | A method used to digitally represent sampled analog signals. |
| R2R | Reel to Reel tape player or Resistor to Resistor type DAC. | A DAC based on an electrical circuit made from repeating units of resistors. Often referred to as a ladder DAC. |
| RCA | Radio Corporation of America | The ubiquitous RCA analog audio connector. |
| RMS | Root Mean Square | The continuous (or music) power that the amplifier can deliver. |
| SACD | Super Audio CD | High-resolution disc format created by Sony and Philips. |
| SBC | Low-complexity Subband CODEC | A medium quality Bluetooth digital audio CODEC for devices like headphones or loudspeakers. |
| SPC | Silver Plated Copper | Wire composed of a copper core covered by a silver plating. |
| SINAD | Signal-to-Noise and Distortion Ratio | The ratio of the total signal power level (Signal + Noise + Distortion) to unwanted signal power (Noise + Distortion). Higher is better. More often used in DAC measurements than SNR. |
| SNR | Signal-to-Noise Ratio | A measure that compares the level of a signal to the level of background noise. |
| S/PDIF | Sony/Philips Digital Interface | Coaxial or optical digital audio connection. |
| THD+N | Total Harmonic Distortion + Noise | Total Harmonic Distortion is the sum of all the harmonic distortion products in a measurement. THD+N adds noise to this figure. |
| TOSLINK | Toshiba Link | A common digital optical connector system. |
| TRS | Tip Ring Sleeve | 3-pole unbalanced stereo connector - 6.35 (¼”) or 3.5mm (⅛”). |
| TRRS | Tip Ring Ring Sleeve | 4-pole connector - unbalanced 3.5mm (⅛”) or balanced 2.5mm. |
| TWS | True Wireless Stereo | Bluetooth device function allowing for stereo sound in devices without any external or connecting wires. Typically associated with small IEMs like the Apple Airpods. |
| UAC | USB Audio Class | Standards for USB device compliance, including classes 1, 2, and 3. |
| USB | Universal Serial Bus | A data transfer protocol where the USB-host, initiates a transfer and the devices respond to the host. |
| WAV | Waveform Audio File Format | Developed by Microsoft and IBM, and is the standard CD format encoding method. |
| WMA | Windows Media Audio | A series of proprietary audio codecs developed by Microsoft. |
| VBR | Variable Bit Rate | A method of encoding lossy audio files where the bit-rate fluctuates depending on the requirements or complexity of the audio. |