Period sound: how each decade's audio is made
A home movie from the 1970s doesn't only look like the 1970s. It hums like a cine camera and hisses like magnetic stripe. The sound of each decade is worked out the same way as its picture.
Sound follows the decade
The picture changes with every technology and style. The sound changes with the decade: there is one sound recipe for each of the fifteen, written from the machine that ordinary people would most likely have recorded on, from a wax cylinder phonograph to a phone with several microphones.
Home movie cameras recorded no sound at all until sound Super 8 arrived in the 1970s. The earlier recipes are a deliberate anachronism: your voice as it would have sounded on the recording machines of the same years, from the cylinder and the disc to wire and reel-to-reel tape.
The chain
With SOUND on PERIOD, the microphone signal goes through these steps, in this order, while you record:
- The band. Every medium had a lowest and a highest frequency it could hold. A wax cylinder kept roughly 250 to 2,500 Hz: no bass, no sparkle, only the middle of the voice. Over the decades the band widens until it covers everything you can hear. The app cuts off the lows and the highs at the recipe's limits.
- The resonance. Horns, diaphragms and small speakers boosted some frequencies more than others. Most recipes add their own peak in the middle of the voice, without making it louder overall.
- Wow and flutter. A cylinder, a turntable or a tape motor never ran at a perfectly steady speed. A slow waver (wow) and a fast one (flutter) bend the pitch slightly. It is strongest on the early cylinders, gentle on tape, and gone with digital.
- Distortion. Loud sounds overloaded the cutting stylus or saturated the tape, and the peaks rounded off. The app softly clips the signal, more for the mechanical and magnetic media.
- Digital crunch. The 2000s camcorder recipe reduces the resolution of the signal slightly, for the hard edge of early digital audio.
- Dropouts. A worn patch of tape or wire loses the signal for a moment. Now and then, about 30 milliseconds of sound disappear.
- The noise bed. Underneath your voice the app adds the sound of the medium itself, generated fresh as you record: the surface hiss and crackle of cylinders and discs, the mechanical ticking of the early machines, a low 50 Hz hum under the recipes of the 1890s to the 1940s, the hiss of tape, and the motor of a cine camera or camcorder.
The file is recorded in mono, as AAC audio, at your clip's real speed: nothing is sped up or slowed down.
The three SOUND modes
- PERIOD (the default): your voice through the decade's chain, with the noise bed underneath.
- SILENT: no voice, only the bed. A silent reel is never really silent: you hear the mechanism, the crackle or the tape hiss. In the 2010s, 2020s and 2030s the medium is digital, so SILENT is true silence.
- ORIGINAL: your iPhone's audio exactly as it was recorded, untouched.
Tap the SOUND mini-button to cycle the modes, or use MENU › SOUND › AUDIO. The icon turns orange whenever you are not on PERIOD. While you record, the bed also plays quietly through the speaker so you can hear the decade around you: MENU › SOUND › SPEAKER FX sets how loud, from OFF to HIGH.
DEGREE and sound
DEGREE uses the same curve on the sound as on the picture. It scales the noise bed, the distortion, the wow and flutter, the digital crunch and the dropouts. It never changes the band, because the band is the medium. A 1920s disc at DEGREE 1 is quiet and steady but still has no bass. See DEGREE.
The fifteen recipes
The band, the noise bed and the wow and flutter of each decade, from the app's sound recipes. The last column is what SILENT leaves.
| Decade | Recipe | Band | Noise bed | Wow · flutter | SILENT |
|---|---|---|---|---|---|
| 1890s | Wax Cylinder Phonograph | 250 Hz – 2.5 kHz | mechanical ticks, hiss, crackle, 50 Hz hum | 1.2% · 0.5% | the bed |
| 1900s | Early Acoustic Phonograph | 220 Hz – 2.8 kHz | mechanical ticks, hiss, crackle, 50 Hz hum | 0.9% · 0.4% | the bed |
| 1910s | Acoustic Disc Recording | 180 Hz – 3.2 kHz | mechanical ticks, hiss, crackle, 50 Hz hum | 0.7% · 0.3% | the bed |
| 1920s | Late Acoustic / Early Electrical Recording | 150 Hz – 4.5 kHz | hiss, crackle, 50 Hz hum | 0.5% · 0.2% | the bed |
| 1930s | Electrical Disc Recorder | 100 Hz – 6 kHz | hiss, crackle, 50 Hz hum | 0.35% · 0.15% | the bed |
| 1940s | Early Portable Wire Recorder | 120 Hz – 6.5 kHz | hiss, crackle, 50 Hz hum | 0.6% · 0.35% | the bed |
| 1950s | Home Reel-to-Reel Recorder | 80 Hz – 9 kHz | hiss | 0.35% · 0.2% | the bed |
| 1960s | Portable Cassette / Tape Recorder | 100 Hz – 8 kHz | hiss | 0.45% · 0.3% | the bed |
| 1970s | Super 8 Magnetic Sound | 100 Hz – 7.5 kHz | hiss, camera motor | 0.4% · 0.25% | the bed |
| 1980s | VHS Consumer Camcorder Audio | 80 Hz – 8 kHz | hiss, camera motor | 0.25% · 0.12% | the bed |
| 1990s | Hi-band 8 mm Camcorder Audio | 50 Hz – 15 kHz | hiss, camera motor | 0.02% · 0.01% | the bed |
| 2000s | Mini DV Digital Camcorder | 40 Hz – 19 kHz | hiss, camera motor | none | the bed |
| 2010s | Early Smartphone Audio | 100 Hz – 16 kHz | hiss | none | silence |
| 2020s | Modern Computational Smartphone Audio | 50 Hz – 19 kHz | none | none | silence |
| 2030s | Future Computational Audio | 20 Hz – 20 kHz | none | none | silence |
Tips: record someone talking in the 1890s and again in the 1950s, and listen to sixty years of engineering open up the voice. For a 1970s home movie, try SILENT: you keep the camera motor and the hiss, and lose the voices that a silent Super 8 camera would never have caught.
Listen to all fifteen
The same line through each decade's chain, rendered by the app's own audio code at DEGREE 7, with ORIGINAL for comparison.