Final Recordings

Been very busy since my last post, I will write up in more depth at some point but so far I've conducted one or two more tests in a slightly larger studio which illustrate the stereo effects much more clearly which is good.

Spaced Omni Pair, ORTF and Mid Side Techniques

Last night I completed the first of my final recordings with a local clarinet quartet who were fantastic. I had a few technical problems with only one of the Pro-Tools interfaces seeming to work, so I wasn't able to have spot mics as well as my stereo arrays but the recordings from the arrays sound great. The C414s were clear and quiet while there was a bit of noise from the C451b's. I have, once again, fallen in love with the Blumlein technique, it gives a really clear image which is balanced and tonally pleasing :-)

I will be completing one more recording, with a string quartet, next Wednesday before I conduct listening tests with a small group of people to find out which techniques people prefer on playback.

Continuing Experiment and Research

Since my last entry I have been into the studio to conduct some more experiments.
The first using CLIO, an electrical and acoustic measurement system, I played pink noise from a speaker at a number of different stereo arrays and measured the dBSPL from each microphone in the array for two different locations of the speaker- directly in front and 2 meters off to the side. By comparing the difference between levels for the pair of microphones the ability of each technique to localise sound based on level differences could be assessed. 


The next experiment involved setting up the microphone techniques one at a time and playing a short burst of sound from 4 different locations within the room. These signals were recorded into Pro-Tools and then later by zooming in and using the selector tool to measure the difference in samples between the two microphones within a pair the time difference was calculated. This gave some interesting results showing which techniques use time delays for localisation.


The combination of these two experiments have led me to choose a different room for my final recording, although I would like to use the SSL AWS 900 that comes with the room, it just isn't wide enough to get a large enough stereo field. I've spoken to some local string groups and it seems I will be creating my final recordings at some point in mid march.


My research is continuing, now moving forward to investigate the processes involved with reproducing stereo sound. Today I have been focusing on loudspeakers and the problems of acoustic crosstalk as well as reading a lot about transaural stereo- the process of recreating three dimensional virtual sound sources all around the listener using just two sound sources located infront of the listener. It's very clever but the research indicates it sounds quite unnatural to the listener and tends to cause fatigue pretty quickly. 
Tomorrow I will move onto investigating binaural and headphone stereo, I've already found some fascinating albums recreating Rachmaninov piano concertos recorded in both standard stereo and binaural and the differences between them are striking.  

Progress Report

It's been a while since I've last posted, which isn't to say I haven't been doing work, I just had a lot of other deadlines just before Christmas pushing my dissertation onto the back burner. Now that 2011 is here I've spent the last week putting together my progress report detailing to my tutor exactly what progress I have made, where I'm behind and how my time plan is being adjusted to make up the difference.

Most of the research into microphone techniques is now complete, so I can now move onto researching some methods of reproducing stereo images- over headphones, speaker systems etc. and the processing that goes on to create a coherent image. I will also be investigating the artificial creation of stereo recordings through pan pots, delays and assorted plugins.

This Thursday afternoon will be the first of my experiments into the researched techniques. I will be setting up several techniques simultaneously and then recording sound sources at various points throughout the field, varying the angles of the microphones and the distance from them to gauge the effect this has on the image.
The microphones and techniques I will be investigating are:

Technique	Polar Pattern(s)	Microphones
Co-incident Pair: Blumlien	Figure of 8	AKG C414 x2
Co-incident Pair: XY 90° hypercardioid	Hypercardioid	AKG C1000s x2
Co-incident Pair: XY 180° cardioid	Cardioid	AKG C451 x2
Co-incident Pair: Mid-Side	Figure of 8 Cardioid	AKG C414 Neumann TLM103
Near co-incident Pair: ORTF	Cardioid	AKG C414 x2
Near co-incient Pair: NOS	Cardioid	Matched pair Rode NT1A
Spaced Pair	Omni-directional	Audix TR40 x2
Binaural		Soundman in ear mics
Surround Sound		Holophone H3-D

I will post some pictures and perhaps a few samples soon.