I plan to study three methods of stereo sound recording, establishing the benefits and disadvantages of each, hopefully arriving at recommendations for different needs.

The methods covered are: -

1. Blumlein – usually a pair of cardoid response mics placed in close proximity, with an angle between inserts of 90 to 120 degrees
2. RCA – usually a pair of Omni response mics placed several metres apart on a line square to the sound source.
3. Binaural – usually a pair of Omni response mics mounted in a dummy head.

Diagram 1

The different factors being evaluated are: -

1. Ability to capture directional information in a horizontal (flat) plane (pantophonic information)
2. Ability to capture ambient information of the listening environment
3. Ability to capture directional information in a spheroid plane (periphonic information)
4. Suitability for being reproduced on speakers.
5. Suitability for being reproduced on headphones.

The brain interprets directional information from three different clues, which I will handle separately.

Interaural Time Delay (ITD) is the time delay between the ears receiving a sound that is not equi-distant from them. (pantophonic)

Interaural Level Difference (?) (ILD) is the difference in volume of signals that are not equi-distant from the ears. (pantophonic)

Head Related Transfer Function (HRTF) is the differences in frequency response of the ears to sound from different directions. (periphonic)