Wednesday, December 27, 2006

Anthony Lopez: Styro Head Test

As I said in my previous post, I really enjoyed the Styro head with the EM158 omni mics. This rig seemed to be the most accurate in every aspect: localization, depth, and architectural mapping. There are three tests with stryo heads, and of the three, T4-10 is the most successful. For reiteration, here is my edited previous description of the rig in regards to localization, depth, and architecture.

T4-10 Styro Head EM158 Omni Mics.

A) This rig does an excellence job of recreating localization for the human head. When I close my eyes, without looking at the graphic, each clink has a physical presence in my ears and is easily mapped out. Because the capsules are front facing they seem to favor 10-2 o’clock, which makes it harder for me to discern the location of these because the clinks are more immediate and are being amplified by the shape of the head, in much the same way the boundary insets effect the sound on a parallel boundary mic. Here is a comparison of the two rigs for clarification.


Both of these tests display a lot of space and easy localization. However, I think the styro head provides the most.

B) When comparing the depth of the parallel boundary and the styro head, the styro head seems to have a more realistic sense of depth; although, the parallel comes close. Sometimes the depth seems difficult to discern because of the variable amount of force that was used to clink the nails. The clinks sound further away at 8, 3, and 4. And closer at 9, 10, and 11. At 12 the rig seems to have the correct depth. This is perhaps due to the 6” headspace on the foam head allowing the stereo image of the sound to reach both ears properly. At the other positions the opposite capsule becomes a victim of head shadow, something the human head experiences, which causes one ear/capsule to receive more sound sooner than the opposite one.

The main difference between these two rigs is the type of boundary they offer. The parallel has a dense, flat, wooden boundary. The styro has a foam, curved boundary. As has been suggested by Rob D. in class, the curve of the head allows some sound frequencies to roll off easier. As opposed to the square wooden boundary which tends to amplify the frequencies by about 6dB (click to see diagram). One solution, suggested by Curt Olson, is to cut off the edges off the corners of the parallel rig in order to simulate the relative space and shape provided by the human head. The difference in these two mics can be heard in the video comparison. Particularly in terms of amplification. As I explained to Rob, the parallel boundary seems almost like compressed sound. The reverberation seems cut-off and the overall sound seems to have less decay and more presence; compare this to the styro head which seems to allow more decay and reverberation to be present; perhaps due to the differences in the shape of the boundaries.



However, one problem with this rig is that the human ears are actually side facing, with the ear cartilage acting as a sound collector, while the capsules are front facing. It would have been interesting to create a test with some kind of ear-apparatus attached to it like an ear.


C) This rig does an excellent job of mapping out the architecture of the space. When I listen to this I can pretty much visualize where every wall was. I know that 8 sounds much further away because there is a lot of dead space behind that area, with a wall much further from the “clinker” than any other position. From 9-12 there is a wall directly behind the clinker, 9 sounds like it is further from this wall though, and 11 sounds very sharp, like the clinker was standing in corner with all the sound being collected and focused before being bounced back. This person was also standing near the car which could have being reflecting a lot of sound. 12 o’clock sounds perfect. The capsules are facing forward and the clinker is in front of a large wall, so the sound is thrown right back. 1-4 positions mimic the 8-11, but with less volume, perhaps because the clinkers used less force, or because there was more space, particularly at 3 where there was a huge depression in the room where the loading dock was, this clink seems to travel for a while, perhaps the longest on this rig.

I have created a comparison video containing the clinks from clock positions 2-4 in order to compare the depth differences in the position, which I think has the most noticeable depth. This video contains comparisons of the 2-4 clock positions from the following tests: T5-Dead Center (styro head), T4-10 (styro head), T4-2 (styro head), and T5-3 (parallel boundary). The point of this test is to draw comparisons of the same rig at 3 different positions, and to give a comparison to the parallel boundary.

Test Link

In this video, the styro head tests have an obvious spaciousness at the 3 o’ clock position. As I explained earlier, this is where the depression in the room where the loading dock is. Because there is more space for the sound to reverberate in, the clink sounds more distant than the rest of the clinks. Compare this to the 3 o’clock position of the parallel boundary in which the sound loses this quality because of the amplification of the boundary on parallel.

All of the styro tests sounded pretty close, however, I still think T4-10 was the most successful. I get the best sense of depth, localization, and architecture from this rig. I think that any immediate differences in the quality of the styro head rigs was perhaps due to the variations in force used by the clinkers.

1 comment:

us said...

HI Anthony L--
I find your descriptions of the advantages of the StryoHead rig quite good-especially that the left and right channels seem more unified, the reverberations are a tad more precise and its a less less bifurcated than the Parallel Boundary.

Why this is happening is the pursuit.

Was it possible in your comparison of the StyroHead to the Parallel Boundary rigs to use the same test/ sound stimuli? It looks like there are several parallel boundary tests on test four and you used test five for the parallel sample?

When I study http://pantherfile.uwm.edu/adlopez/public/styro_parallel.mov , I find the Parallel Boundary rig does a better job with localization on the left side of the field and the StyroHead is more impressive on the right. Note how 8 o-clock has a decay that seems to come from 12 o-clock on the StyroHead rig. Both rigs are challenged to define 3 and 4 as further back of 2. There's a more noticeable jump between 1 and 2 on the Parallel boundary rig where the transition between 12-and 2 is smoother on the Styrofoam. We're in agreement for the most part regarding the right side of the field.

The jerkiness in the flow of http://pantherfile.uwm.edu/adlopez/public/3tests_2-4.mov is making it hard to use this test. I'm not sure what I'm listening for. The effects of capsule orientation? Try to place material from the same test back to make comparisons easier.

Your suggestion of adding ears to the StyroHead is a good one. Is it like adding a small double boundary perhaps? One that blocks more of the sound coming from the rear too?

Tests could also be done on progressively rounding the wooden boundary and even making it smaller. I felt that insets of .5" and 1" created a more spatial stereo field than those of 2.5" so perhaps there's a good argument for making a parallel boundary rig more head-shaped in several respects?

That its not easy to discern the differences in these rigs and placements is perhaps significant too, Its a common complaint that binaural recordings (like those of the StyroHead) don't have enough "contrast" between the left and right side to hold up when played over loud speakers. Binaural recordings require that the speakers be close and nearly oppositional-- 180 degrees. I wonder what both rigs would sound like when played back on stereo speakers with a 90-120 degree spread rather than 180 degrees?

If we did the test again, we'd run a continuous StyroHead fixture for comparison throughout the test. No one expected it to work so well. This is a good example of why a rigorous test can produce evidence that would otherwise take years to acquire. Good job. Rob D.