The Sound of Electricity
Thirty recordings of static, buzz, hum and continuous current, picked up directly from electronic devices with custom-built coil microphones at 96 kHz.
Electricity is a strange thing to record. There is no single source you can point a microphone at, no acoustic event in the usual sense. What you hear in a buzzing transformer or a coil-whining laptop charger is a side effect: the electromagnetic field around a conductor causing something nearby (a transformer lamination, a capacitor, a piece of plastic, the human ear via an unshielded amplifier) to vibrate at a multiple of the line frequency. The clean way to record electricity is therefore not to record the air at all, but to listen to the field directly.
For this collection, custom-built coil microphones were used to do exactly that, picking up the field around the conductors of various electronic devices: phones, server racks, laptops, hard disks, fuse boxes, refrigerators, lamps, monitors and a few good old wall outlets. Some of the resulting files were then processed further with software and a Eurorack modular system to push them in directions a raw recording cannot reach. The full set is thirty files, around a minute each, totalling twenty-seven minutes of audio.
The sources
-
Mains and the wall outlet
Plain household current at the standard line frequency, with the characteristic low sinusoid and its first few harmonics. The reference point of the collection: everything else can be measured against the steady tone of an unloaded outlet.
-
Mobile phones and data streams
Smartphones in active use produce a recognisable cluster of bursts, clicks and digital crackle as they exchange data with cell towers and Wi-Fi access points. These are not acoustic at all in their original form: the phone is silent in the room, but a coil microphone next to it lights up with intermittent rhythmic patterns whenever a packet goes out.
-
Server racks, laptops and hard disks
Computers radiate a constantly shifting field at the switching frequencies of their power supplies and CPU regulators, plus a layer of slower modulation tied to disk activity. Hard disks add their own distinct content: tonal stepping when the head moves, broadband rush during sustained reads.
-
Fuse box and refrigerator
The fuse box gives a loaded mains tone with extra harmonic complexity from the breakers and the connected loads in the building. The refrigerator adds a slow compressor cycle on top of a steady inductive hum, useful as a base for room beds and ambient drones.
-
Lamps, monitors and chargers
Lamps and monitors contribute the higher-frequency end of the collection: switch-mode power supplies, backlight inverters and dimmer circuits produce thin tonal whines, choppy buzzing and audible flicker tones, often shifting in pitch with load.
-
Designed and processed variants
A subset of the recordings was processed further, both with software and a Eurorack modular system, to add character and depth. These designed variants stay rooted in the original source material but extend it for sound design use, with seamless looping and heavier shaping than the raw captures.
"SHAPINGWAVES has assembled unique library material that pushes each one of its categories to the next level."
What you are actually hearing: a short primer on the sound of electricity
Mains hum is not one tone, it is a comb
The familiar electrical hum is built around the line frequency of the local grid: 50 Hz across most of Europe, Africa and Asia, 60 Hz across most of the Americas. What we hear in a transformer or fluorescent lamp is rarely the fundamental alone. Magnetostriction in the steel core of a transformer causes the laminations to physically expand and contract twice per cycle, producing a strong second harmonic at 100 or 120 Hz, plus higher-order odd harmonics that ride on top. The result reads as a buzz rather than as a clean tone, and the harmonic balance is what gives different transformers and ballasts their individual character.
| Region | Line frequency | Dominant audible component |
|---|---|---|
| Europe, Africa, much of Asia | 50 Hz | ~100 Hz second harmonic, with 150, 200, 250 Hz partials |
| Americas, Japan (east) | 60 Hz | ~120 Hz second harmonic, with 180, 240, 300 Hz partials |
Coil whine and switch-mode power supplies
Modern electronics rarely run from raw mains. Almost everything passes through a switch-mode power supply that chops the input current at frequencies between roughly 20 kHz and several hundred kHz, well above the audible range, then filters it back into smooth DC. The chopping is silent in theory, but inductors and ceramic capacitors in the supply flex slightly under the high-frequency current and emit a faint sound at audible subharmonics or at modulated frequencies that drop into the audio band as load changes. This is what is heard as "coil whine" in a laptop or a graphics card. It is also what makes switching supplies so easy to record electromagnetically: the same field that excites the components also drives a coil microphone hard.
Why a coil microphone hears what an air microphone cannot
An ordinary microphone responds to changes in air pressure. A coil microphone responds to changes in magnetic flux, which means it picks up the field around any current-carrying conductor regardless of whether that field translates into sound in the room. Two consequences follow. First, the coil microphone is most sensitive when placed close to a conductor with a fast-changing current: a power supply, a digital data line, the back of a mobile phone during a transmission. Second, the recording exposes content that simply has no acoustic counterpart, such as the rhythm of a phone's GSM bursts or the switching pattern of a server's voltage regulator. This is the core technique behind the collection.
Digital traffic as audio
Digital communication is, from an electromagnetic point of view, a structured form of noise. Packet rates, clock divisions and protocol-level patterns leave audible fingerprints when picked up via a coil. A keyboard scanning its matrix, a Wi-Fi card beaconing every hundred milliseconds, a hard disk seeking, a CPU switching power states under load: each of these has a characteristic rhythm. In the collection, these patterns appear as periodic clicks, rhythmic bursts of crackle and slow modulations on top of the underlying hum.
Why some files reach above 20 kHz
Recording at 96 kHz / 24 bit gives a usable bandwidth up to about 48 kHz. With electrical sources, a lot of useful structure sits above the standard 20 kHz audio limit, particularly the lower harmonics of switching supplies and the first sidebands of digital traffic. Pitching the material down brings that content into the audible range cleanly, which is one of the reasons the recordings hold up well under heavy processing.
How the material is typically used
In post, this kind of source material falls into a few common buckets. As atmospheric beds, where a mains hum or a server-room layer sits underneath a scene to anchor an interior. As a base for sound design, where a coil-microphone capture pitched two octaves down becomes a drone, a power core or a creature hum. As transitional or interface material, where a digital crackle or a switching whine reads as data activity, error states or technology in action. And as transient detail, where a short burst from a phone exchange adds a layer of life to an otherwise static room tone.
- Recorder
- Sound Devices MixPre-6
- Microphones
- Custom-built coil microphones
- Additional processing
- Software and Eurorack modular system on a subset of files
- Sample rate / depth
- 96 kHz / 24 bit
- File count
- 30 WAV files, around 1 minute each
- Total audio
- 27 minutes
- Download size
- 730 MB
Cataloguing: UCS and forty languages
Every WAV in the collection follows UCS 8.2.1 naming and carries more than twenty fields of embedded metadata, written into BWAV, iXML, LIST/INFO and Soundminer chunks: CategoryFull, Category, SubCategory, CatID, FXName, Description, BWDescription, CDDescription, CDTitle, Recordist, Designer, Artist, Manufacturer, Publisher, Source, URL, VendorCategory, ixmlNote, OpenTier, LongID, ShortID, Library, Keywords, TrackTitle, Microphone, Location, MicPerspective, RecMedium, RecType, Track, Version, ISRC.
The descriptive fields (Description, BWDescription, CDTitle, TrackTitle, CDDescription, FXName and Keywords) are translated into forty languages, including Arabic, both Chinese variants, French, German, Hindi, Japanese, Korean, Portuguese, Russian, Spanish, Turkish and Vietnamese, and ship as TSV and XLSX sidecars next to the audio. The collection lives under the UCS category ELECTRICITY-BUZZ & HUM.
"The ShapingWaves collections are full of extremely well recorded, professionally catalogued dynamic sounds. SHAPINGWAVES has assembled unique library material that pushes each one of its categories to the next level, very useful for sound designers everywhere."
Wylie Stateman, Sound Designer (Deepwater Horizon, Shrek, Kill Bill 1+2, Tron)"ShapingWaves is a place I go to when I need an obscure and/or well recorded sound source. Very cool stuff!"
Matt Temple, Sound Supervisor (The Passion of the Christ, The Office)"Keep up the good work. It's much more fun being a sound designer these days because of independent sound libraries like yours."
Peter Albrechtsen, Sound Designer (Antichrist, Cathedrals of Culture)The work documented here lives on as the Circuits sound library, distributed as a 730 MB download of thirty 96 kHz / 24 bit WAV files with full UCS metadata, under the SHAPINGWAVES License Agreement for use in film, television, games and other media productions.