Terms related to sound technology are explained here
- A common method for generating sound electronically on a PC. Output is produced using a table of sound samples -actual recorded sounds – that are digitised and played back as needed. By continuously rereading samples and looping them together at different pitches, highly complex tones can be generated from a minimum of stored data without overtaxing the processor.
- Waveform Audio: the native digital audio format used in Windows. WAV files use the .wav file extension and allow different sound qualities to be recorded. Either 8-bit or 16-bit samples can be taken at rates of 11025Hz, 22050Hz and 44100Hz. The highest quality (16-bit samples at 44100Hz) uses 88KB of storage per second.
- The conversion of spoken words into computer text. Speech is first digitised and then matched against a dictionary of coded waveforms. The matches are then converted into text as if the words were typed on the keyboard.
- A fibre optic digital audio connection used to connect a digital source component (e.g., DVD player, CD player, etc.) to a receiver or pre-amplifier. By passing the “raw” digital audio signal using laser (light) pulses, interference and degradation are minimised. The means of interconnect used for connecting MiniDisc players to stereos and certain sound cards.
- Telephony Application Programming Interface: permits Windows applications to program telephone-line-based devices such as modems and fax machines in a device-independent manner.
- Also called sound board and audio adapter, this is an expansion board that records and plays back sound, providing outputs directly to speakers or an external amplifier. The de facto standard for sound card compatibility in PCs is Creative Labs’ Sound Blaster.
- A family of sound cards from Creative Labs. The Sound Blaster protocol has become the de facto audio standard for PCs. Monaural versions of Sound Blaster cards were introduced in 1989, and a stereo version three years later. The Sound Blaster AWE32 and AWE64 are 16-bit sound cards that provide WaveTable MIDI with 32 and 64 voices respectively.
- Software for recording and editing MIDI files.
- Secure Digital Music Initiative: A secure digital format for distributing music over the Internet. Announced in February 1999, it is backed by the Recording Industry Association of America (RIAA) and Sony, Warner, BMG, EMI and Universal – the top five music production companies. At the time of its announcement, the new format was expected in products by Christmas 1999.
- In digitising operations, the frequency with which samples are taken and converted into digital form. The sampling frequency should be at least twice that of the analogue frequency being digitised. Thus, the sampling rate for hi-fi playback is 44.1kHz, slightly more than double the 20kHz frequency humans can hear.
- The first step in the process of converting an analogue signal into a digital representation. This is accomplished by measuring the value of the analogue signal at regular intervals called samples. These values are then encoded to provide a digital representation of the analogue signal.
- Sony/Philips Digital Interchange Format: an interface standard that lets users connect sound equipment (such as sound boards and speakers) via a pure digital signal.
- Roland General Synthesiser and General MIDI are two overlapping specifications for defining the standard sets of MIDI sounds that are associated with specific commands.
- The name given to the specialised software that extracts raw audio data from a music CD. The ability to extract audio digitally relies on a feature of newer CD-ROM drives that allows the digital data from audio CDs to be passed through the computer’s bus (IDE, SCSI) just like CD-ROM data.
- The sum of all sound reflections in a given environment.
- Sounds that originate from a sound source and bounce off walls, floors, ceilings and other obstructions before reaching the listener.
- Extreme audio compression scheme used on the Internet to provide streamed audio over ordinary modems
- The study of how the human brain perceives sound. Findings relating to which sounds are and are not heard by the human ear have been used in the formulation of various audio compression techniques, including MP3.
- The number of voices a synthesiser can play at any one time.
Physical Modelling Synthesis
- A revolutionary method for generating sound. This technique emulates the impulse patterns of real-world instruments using a software model.
- Sounds that originate from a sound source behind a wall or door or other solitary object. In so doing, they are subtly altered – usually with a volume drop and muffling, depending on the material and thickness of the obstruction.
- Even when sounds originate in the same room, they are often obstructed by objects like furniture before they reach a person’s ears. However, because the sound remains in the same room as the listener, the reverberation effect on these sounds will not be muffled – reverberation will spread round a whole room regardless of individual obstructions.
- The number of simultaneous instruments a synthesiser can play.
- Supplies up to five full bandwidth channels (left, right, centre, and two surround channels), plus an additional low frequency enhancement channel, and/or up to seven commentary/multilingual channels. The MPEG-2 Audio Standard will also extend the stereo and mono coding of the MPEG-1 Audio Standard to half sampling-rates (16 KHz, 22.05 KHz, and 24 KHz), for improved quality for bitrates at or below 64 Kbits/s, per channel.
- MPEG defined three levels or layers of audio compression. Which layer a type of equipment uses depends on the desired level of compression. These three layers compress audio data streams by roughly four, six and eight times respectively, around 64, 128 and 192Kbit/s per channel. In practical terms, these compression rates make possible radio broadcasting of CD-quality music. All three layers are defined for both monaural and stereo sound. Definitions for surround sound and other high fidelity applications are under consideration.
- Standardised as ISO-MPEG Audio Layer-3 (IS 11172-3 and IS 138-3), MP3 employs a lossy compression technique, with bits of information being discarded to allow data to be compressed into files which are relatively small in comparison with WAV files but which retain subjective CD quality.
- MD: a compact digital audio disc from Sony that comes in read-only and rewritable versions. Introduced in late 1993, the MiniDisc has been popular in Japan. The read-only 2.5in disc stores 140MB compared to 650MB on a CD, but holds the same 74 minutes worth of music due to Sony’s Adaptive Transform Acoustic Coding (ATRAC) compression scheme, which eliminates inaudible portions of the signal.
- Windows multimedia translator for MIDI hardware and software.
- Musical Instrument Digital Interface: a specification that standardises the interface between computers and digital devices that simulate musical instruments. Rather than transmit bulky digitised sound samples, a computer generates music on a MIDI synthesiser by sending it commands just a few bytes in length. These contain all the information a sound board needs to reproduce the desired sound – the type of instrument, the pitch, duration, volume, attack, decay, etc. are all specified by the protocol. Each channel of a MIDI synthesiser corresponds to a different instrument, or “voice”. Programming several channels simultaneously produces symphonic sound.
- Head-Related Transfer Functions: Refers to the mathematics that models the way a human ear localises the direction of a sound.
- A table of 128 standard sounds or instruments for MIDI cards and synthesisers.
- The increase in signalling power as an audio signal is boosted by an electronic device. It is measured in decibels.
- Frequency Modulation Synthesis: an outdated technique for synthesising music reproduction but still widely supported to provide compatibility with older games software.
- Environmental Audio Extensions: a hardware and software audio standard developed by Creative Labs. And used originally in the company’s SoundBlaster cards. EAX has subsequently become a widely supported standard offering 3D positional audio and allowing the manipulation of sounds so that they can appear to be heard in different listening environments.
- The DVD audio-only storage format similar to CD-Audio. DVD-Audio is facing stiff competition from a number of other high fidelity audio standards.
- A digital audio encoding system from Dolby used in movie and home theaters. First used in 1995, Dolby Digital employs Dolby’s AC-3 (Audio Coding-3) coding and compression technology and provides six channels of audio, known as 5.1 for front left, front right, front center, rear left, rear right and subwoofer.
- A perceptual digital audio coding technique capable of delivering multichannel digital surround sound. It incorporates 6 (5.1) discrete channels; each channel can carry a different signal simultaneously (left front, right front, centre, left rear, right rear, sub-woofer).
- A doubling effect used to enhance sound.
- Unix sound file format popular on the Internet.
- Audio Interchange File Format: used for high end audio applications.
- An Intel-recommended standard for PC audio circuitry. The specification reduces noise by partitioning analogue and digital components into separate modules.
- A positional audio technology and audio API developed by Aureal Semiconductor Inc. A3D enables a real-life audio experience by surrounding the listener with sounds in all three dimensions using only a single pair of ordinary speakers or headphones.
- A unit of measure that indicates the resolution of a digitised sound sample. The higher the resolution, the better the audio fidelity. Audio that is digitised using 8 bits of resolution is slightly better in fidelity than normal AM radio.
- A blanket term for technologies that alter the way sound is distributed in real-world space. Spatialisation broadens the soundstage (the area in space where the sound seems to be coming from), making it more dramatic and spacious, and gives the illusion of pushing it beyond the physical location of the speakers. Positional audio uses encoded audio streams to position sounds realistically in the space around the listener when the sounds are played back on compatible equipment.
- A unit of measure that indicates the resolution of a digitised sound sample. The higher the resolution, the better the audio fidelity. 16-bit audio is the standard used for standard audio Compact Discs (CD-DA).
- Yamaha’s extension of General MIDI that provides many instrument variations and more digital effects. Many instrument parameters can be controlled in real-time.
- Recording Industry Association of America: The association formed by the recording companies in the United States to promote the recording industry and to defend its legal rights. The RIAA equalisation curve is a compensation method applied to a signal from a record deck pick-up. Phono pre-amps have RIAA circuitry built-in.