Spatialisation and surround sound Flashcards
How have the ears of humans and animals evolved?
- Humans (and animals) have evolved to be binaural (have two ears), enabling them to detect where a sound is likely to be coming from.
- Having two sources of sound information allows the brain to triangulate where the sound originated.
What do humans and animals use the difference in level to determine?
A sounds rough direction
How does the mass of the head act like a baffle?
The mass of the head creates an acoustic shadow that attenuates the level in one ear, acting like a baffle.
How does the head also help to determine the sound source?
Like any baffle, the head reduces some frequencies more than others (e.g. high frequencies), thus providing even more information to help determine the source.
How does the pinna filter incoming sound?
The pinna subtly filters
sounds from the rear…
(especially high-frequencies) while focusing
sound from the front
into the ear canal.
- This allows us to
target distant sounds
by orienting our head.
Give an example of early spatialisation methods.
Richard Wagner’s Bayreuth Theatre (1876) - Purpose-built venue for Wagner’s ‘Ring Cycle’.
- Orchestra seated behind a screen, arranged to hide the players and balance the sound, allowing Wagner to control how the music was transmitted to the audience.
What were the speakers like for ‘talkies’ in early film sound?
In early film sound, (“talkies”) voices would appear to come from the cinema’s single speaker, which may not be near the image of the speaker on screen.
How were live music performances in cinema different?
Live music performances envelope the audience in sound from multiple sources:
- Performers and instruments at different locations
- Complex reflections off the surrounding walls
Who pioneered stereo recording?
Stereo recording and playback was pioneered in the early 1930’s by Alan Blumlein, working for EMI.
Give 4 innovations that Blumlein introduced with stereo.
- The coincident X-Y (or “Blumlein”) pair arrangement for mics (for recording stereo sound)
- Recording two grooves on records (e.g. vinyl).
- Stereo disc-cutting head
- A transformer to matrix left and right (sum and difference)
How did early recordings make overt use of stereo?
Sounds were positioned as the band appeared on stage
Far L/R (Drums/Bass), Centre (Lead), Far R/L (Rhythm Guitar)
How were early stereo recordings not ‘mono’ compatible?
Centre would appear louder when played back in summed mono or completely cancelled if the speakers were out of phase.
- Hence, studios recorded both mono and stereo versions.
How do modern recordings make more conservative use of stereo?
- Conservative panning
- Must be suitable for radio, portable audio, night clubs, etc.
- Stereo image used to subtly separate sounds in a mix or add spatial effects, texture, atmosphere, or depth.
Linear pan law: what is the formula for L and R?
- L = 1-x
- R = x
What is an issue with the ‘phantom centre’?
- Listener must be equidistant between speakers for centre effect.
- If not, speech may not seem to originate from the image of the actor.
