1. Hearing 2. Stereophonic Sound & The Man Who Invented Stereo 3. The Haas Effect 4. Binaural Recording 5. HRTF 6. Stereo Microphone Techniques Coincident and Non-Coincident Configuration a. AB b. XY c. Mid Side d. Blumlein e. ORTF 7. Further Research

1. Stereo Microphone
Techniques
stuart.jones3@southwales.ac.u
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www.stuartjones.org

2. Agenda
1. Hearing
2. Stereophonic Sound & The Man Who Invented Stereo
3. The Haas Effect
4. Binaural Recording
5. HRTF
6. Stereo Microphone Techniques
Coincident and Non-Coincident Configuration
a. AB
b. XY
c. Mid Side
d. Blumlein
e. ORTF
7. Further Research

3. Hearing

4. • As in the case of vision, our brain presents us with a single fused audio
image.
• We do not hear two sounds with slight time delays, which is what the ears
actually receive.
HEARING

5. HEARING
• Stereophonic, or two-channel, sound popular in "hi-fi" is really something of
a fraud.
• It most certainly is not equivalent to binaural hearing but acts rather as a
pseudo stereo effect.
• It does, however, give an interesting spacial effect.

6. Stereophonic Sound
And The Man Who Invented Stereo

7. The Man Who Invented Stereo
BBC Radio 4 Today Programme - Broadcast August 2008
Image: Alan Blumlein. Available at: http://blog.bowers-wilkins.com/speakers/definitive-guides/a-history-of-binaural-recording/

8. Stereophonic Sound
•In 1931, English electronics engineer Alan Blumlein developed what he called
“binaural sound” now known as stereo sound.
•The sound reproduction systems of the early movies (talkies) invariably only
had a single set of speakers.
•This gave the somewhat disconcerting effect of the actor being on one side of
the screen whilst his voice appeared to come from the other.
•Blumlein declared to his wife that he had found a way to make the sound
'follow' the actor across the screen.

9. The Man Who Invented Stereo
http://news.bbc.co.uk/1/hi/technology/7537782.stm
The Man Who Invented Stereo was broadcast on Radio 4 at 20:00 on Saturday 2 August, 2008
The BBC Website does not broadcast sound in stereo!

10. The Haas Effect

11. The Haas Effect
(or precedence effect)
The Haas effect can be summarised as follows:
• The ear will attend to the direction of the sound that
arrives first and will not attend to the reflections
providing they arrive within 30 ms of the first sound.
• The reflections arriving before 30ms are fused into
the perception of the first arrival. However, if they
arrive after 30ms they will be perceived as echoes.
Angus, J & Howard, D (2009) Acoustics and Psychoacoustics. UK, Elsevier.

12. The Haas Effect
Demonstration Using a Sample Delay Plug In
With a sample rate of 44.1 we can off set one side of the signal by a maximum of
1470 sample before our brain starts to hear two different sounds.
(44100/30ms)

13. Binaural

15. Binaural
• The term ‘binaural’ denotes having or involving two ears
• Binaural works in a similar way as the 3D image. It is a method of recording audio
which uses a special microphone arrangement intended for replay using
headphones
• Binaural recording is a basic two microphone spaced pair technique. Recordings are
made using two omni-directional mikes at the entrance to the ear canals
• This can sometimes be replaced with an artificial ‘dummy head’ replicating human
features

16. Head-Related Transfer Functions (HRTFs)
Neumann KU100 Dummy Head
Provides the brain with changing spectral
characteristics or frequency response
depending on the direction of particular
sounds.
Image: Neumann KU100. Available at: http://blog.bowers-wilkins.com/speakers/definitive-guides/a-history-of-binaural-recording/

17. Head-Related Transfer Functions (HRTFs)
Dummy Head
‘Oscar’ our Soundman OKM Dummy Head
Available from Technicians
Image: OKM Dummy Head. Available at: https://www.kmraudio.com/brands/soundman/soundman-okm-dummy-head.php

18. Head-Related Transfer Functions (HRTFs)
Binaural "in-ear" microphones can be
linked to a portable recorder, bypassing
the need for a dummy head by using the
recordist's own head.

19. Binaural Microphones
Soundman OKM II
We have 1 x set but not on Connect 2
Image: Soundman OKM II. Available at: http://www.soundman.de

20. Stereo Microphone Techniques

21. Stereo Microphone Techniques
• Stereo sound reproduction sounds more natural to us than mono does
• Ambient stereo-miking tends to capture the natural characteristics of an instrument better than
close mono-miking
• It conveys localisation (left-right placement in the stereo field) and, in comparison to mono,
superior depth of field (the sense of distance from the instruments) and a fuller, more accurate
"picture" of the recording space's acoustic properties (including reverberation, diffusion, and other
elements)
Image: Murray Symphony Orchestra. Available at: http://www.murraysymphony.org

22. Stereo Microphone Techniques
Types of Stereo Mic Techniques
To make a stereo recording, you can use one of these basic
techniques:
1. Coincident pair
2. Spaced pair
3. Near-coincident pair
4. Baffled pair

23. Stereo Microphone Techniques
Non-coincident - Timing and amplitude differences
Coincident - Amplitude differences

24. Spaced Pair or Non Coincident Pair (AB)

25. Stereo Microphone Techniques
Spaced Pair or Non Coincident Pair (AB)
• Use 2 x Identical Mics in front of and aimed at the sound source
• Usually Cardioid
• Mics between 2 Feet and 10 Feet Apart
• The greater the distance the more dramatic the sonic result. Be careful not to create a sonic ‘hole’ in the middle.
• Can cause phase issues at all frequencies.

26. Stereo Microphone Techniques
Spaced Pair or Non Coincident Pair (AB)
• The Spaced Pair technique is commonly used in drum overhead microphone placement
• Time should be given to correct placement as this is the most critical part of your overall drum sound
• Always check the phase of the microphones and mono compatibility (i.e. pan both signals centre)
Image: Spaced Pair. Available at: http://silverlakestudio.com/2011/10/26/spaced-pair-drum-overhead-mic-placement/

27. Coincident pair (XY)

28. Stereo Microphone Techniques
Coincident pair (XY)
• Coincident microphones are placed so that their two diaphragms are as close as possible
• Sound waves that reach both mics equally will therefore produce audio signals that are in phase with each other
• The stereo image produced by XY stereo miking technique is very realistic
Image: XY Pair. Available at: http://www.dpamicrophones.com/en/Mic-University/Stereo-Techniques/XY-Stereo.aspx

29. Blumlein Pair

30. Stereo Microphone Techniques
Blumlein Pair
• The pair consists of an array of two matched microphones of bi-directional (figure 8) pickup pattern,
positioned 90° from each other.
• The pickup patterns of the pair, combined with their positioning, delivers a high degree of stereo separation
in the source signal as well as the room ambience.
• The Blumlein pair produces an exceptionally realistic stereo image, but the quality of recordings is highly
dependent on the acoustics of the room and the size of the sound source.

31. Mid-Side Technique

32. Stereo Microphone Techniques
Mid-Side Technique
The MS technique utilises a direction
microphone pointing at the source sound and a
bi directional (figure of 8) microphone to pick
up ambience.
Image: XY Pair. Available at: http://www.audio-production-tips.com/microphone-technique-middle-side.html

33. Stereo Microphone Techniques
MMiidd- SSidied Teec hDniequceoding
Image: M/S Technique. Available at:http://www.blareshare.com/music/recording-tips/how-to-record-an-acoustic-guitar-in-stereo/

34. ORTF
Office de Radiodiffusion Télévision Française

35. Stereo Microphone Techniques
ORTF uses two cardioid microphones with
the capsules spaced 17 centimetres, with
the angle between the microphone
bodies at 110 degrees.
ORTF
Image: ORTF. Available at: http://sv.wikipedia.org/wiki/Fil:ORTF-Stereo.png

36. Stereo Microphone Techniques
ORTF
Yours truly setting up ORTF array for ‘Kids In Glass Houses’ string recording, Atrium 2010.

37. Further Research

38. Further Research
• Think of the studios as laboratories.
• Book 2 x hours in the studio and a basic selection of microphones that can be used to demonstrate stereo recordings (i.e.
a matching pair of small diaphragm condensers and a large diaphragm condenser with selectable polar patterns).
• Practice setting up stereo microphones. This can sometimes be difficult, time consuming and not always practical during a
recording session with time restraints.
• Demonstrate different stereo microphone techniques using a Blumlein style ‘walking across the sound stage’ type
experiment.
• Accurately document your findings using photos, videos and the slate function on the desk to record voice references.
• Listening to your findings using loudspeakers and headphones. Which do you prefer and why? What mistakes did you
make? What would you change if you were to carry out the experiment again?
• Audio engineering in not just about recording bands/music. Your skills as an engineer can only be developed by spending
as much time in the studio as possible and through experimentation.

39. • Abbey Road Studios (2012) The Man Who Invented Stereo. Available at:
http://www.abbeyroad.com/News/Article/22/Alan-Blumlein-the-man-who-invented-stereo (Accessed: 23 Nov, 2012)
• BBC Radio 4 (2012) The Man Who Invented Stereo. Available at:
http://news.bbc.co.uk/today/hi/today/newsid_7538000/7538581.stm (Accessed: 23 Nov, 2012)
• Bowers and Wilkins (2012) A History of Binaural Recording, Nov, 2012. Available at http://blog.bowers-wilkins.
com/speakers/definitive-guides/a-history-of-binaural-recording/
• Calvert, J.B (2003) Hearing. Available at: http://mysite.du.edu/~jcalvert/waves/hear.htm (Accessed: 23 Nov, 2012)
• Papapetrou, Elizabeth (2000). Double Your Pleasure. Available at: http://business.highbeam.com/3374/article-1G1-
63172382/double-your-pleasure (Accessed: 23 Nov, 2012)
• Shankleman, M (2012) Celebrating a Stereo Pioneer. Alan Blumlein. Available at:
http://news.bbc.co.uk/1/hi/technology/7538152.stm (Accessed: 23 Nov, 2012)
• Schmidt, R (2012) Pan Rules. Available at: http://www.rs-met.com/documents/tutorials/PanRules.pdf. (Accessed: 23
Nov, 2012)
• You Tube (2012) AES Oral History. Neville Thiele “On Alan Blumlein. Available at :
http://www.youtube.com/watch?v=acJweM1Q78s (Accessed: 23 Nov, 2012)
• Wikipedia (2012), Alan Blumlein. Available at: http://en.wikipedia.org/wiki/Alan_Blumlein (Accessed: 23 Nov, 2012)
• Wikipedia (2012), Binaural Recording. Available at: http://en.wikipedia.org/wiki/Binaural_recording (Accessed: 23 Nov,
2012)
Web References

40. Book References
• Angus, J & Howard, D (2009) Acoustics and Psychoacoustics. UK, Elsevier.
• Gibson, David (1997) The Art Of Mixing. USA, Mix Books.
• Izhaki, Roey (2008) Mixing Audio Concepts, Practices and Tools. UK, Elsevier.
• Owsinski, Bob (1999) The Mixing Engineers Handbook. USA, Mix Books.
Supporting Material
The Haas Effect Logic Pro 9 Demonstration - Available at https://blackboard.glam.ac.uk

41. Stereo Microphone
Techniques
stuart.jones3@southwales.ac.u
k
www.stuartjones.org

42. © Stuart Jones/University of Glamorgan, 2013. All Rights Reserved. Reasonable academic use is permitted as
long as full references and URL’s are given.
www. stuartjones.org