Noise Floor? What Noise Floor?

For my performance review I thought it would be interesting to compare the self-noise of the electret capsules. I had noticed that the SoundProject Omni's had a slight buzz when I listened closely, so I wondered if there was any such subtle signature sound for each of the capsules. As it turned out, given the "test environment" of the Pieper warehouse, I could scarcely tell the recordings apart. But, just for fun and because I thought we needed another pretty picture on this site, I ran off a comparison sonogram of the four capsule mics side-by-side. It was produced from this recording (Test 5) which shares the same left to right order as the picture (Primo, Shure, SoundPro, Rapid).












In the sonogram, the purple-blues are the loudest frequencies and the yellow-whites are the softest. As the image contests, my ears weren't fooling me - in the droning hum of the warehouse, these capsules sounded practically the same. Any subtle differences might be attributed to the different rigs (headphone, parallel boundary) that these mics were mounted in. There are some small distinctions between the mics in the low freqency range (the fat blue bands) that may indicate that the Primo and SoundPro were a little bit quieter, but if one were to really want to test the noise levels of these mics, It might be best to find an anechoic chamber.

Brennan Alcott

added later:
Rob D's linear sonogram at -90dB to 24K:

click on picture to enlarge

Reflected Sound and Variance (Matthew Engel)

T05 Comparative
The measurement of traveling sound towards two different mics from the same sound source is an interesting way to identify and map out the space used in these recordings. The differences in pitch and overall reception of the sound in the two different mics is interesting because it gives a lot of information about how sound is traveling in this space and how it reflects off certain surfaces to reach the mic locations in the center. To lift a diagram, earlier used by Anthony, this is a good reference of the types of ways mics and mic rigs receive and develop certain sound receptions to create what we hear in much of these recordings, however its more important that we pay close attention to the first image because it defines what is being talked about here. It is a graphic depiction of how direct sound and reflected sound reach the mics from the points in the Pieper barn that we were using.
Using information from Test five, I was able to determine a certain amount of variances and sound differences in the way the sound is received by two similar sources in two different positions. These positions do affect the final out come of the sound reception, but it is easy to determine the difference in the decay of the sound in each. The two different sounds from the points 10 and 2, chosen for their placements in cramped and open spaces, create a totally different sound from the one mic setup to the next. This is because of placement of the mics, the mic quality, the space surrounding the sound source, and the recording circumstances such as gain level. But the most interesting aspect to try and decipher from the recordings is the space around the sound source. This space is important because it is the reflected surface of the sound being produced and it is what creates the spatial anomalies and produces the amount of ambiance in the sound itself to let our ears hear that there is resonance and large or small amount of space surrounding the sound source. These two recordings both being done by types of parallel boundary mic rigs, this comparison develops a greater idea of the recording space then by just listening to one individual recording, and this is attributed to the ambient reception difference in each of the two different mics at their different positions.
To get down to it, the variance of space in point 10 is less because it has an almost immediate reflected sound where as point 2 has a more muted and less active sound because it is in the area of the barn with the most space. The tests have been placed here side by side to see for yourself. They are played at 25% slower speeds in the first set, and then normal the second set. The major differences in sound captured in the slowed down versions are very obvious and represent the variances in spatial reflection rather well. Keeping all the other elemental controls and effects in mind, see if you can hear the reflections and differences caused by this very cold space.

Padrick Dunns: localization Test

For localization I selected six different test rigs. They are tested in groups of
two. Starting with:

13'' spread side-facing capsules w/baffle Em 158 and 21'' spread side facing capsule w/baffle

T01-01 and T03-01

I listened to each one about six time while I drew a circle and placed each mark so I could localize each mark. This goes for all of the tests. At first I did it looking at the computer but it took my attention away from where the sound was really coming from. When I closed my eyes I came up with this conclusion. Starting with the T01-01 13'' spread the separation of the sound was much more clear than the 21'' spread this could be because ot the piece of cardboard in the middle. It seemed that the variation is much different from the T010-01 to the T03-01. The sound from T01-01 has separation and you can tell where each sound is coming from where the sound from T03-01 10-12 degrees is way off they sound like their are on top of each other. Where 12-1 their is a large seperation. In conclusion the sound is much more clear when the mics are closer together in this case.

The next two are:

Front-facing w/Baffle 13'' spread em158 and Front-facing w/baffle 21'' spread em158 mics

T01-02 and T03-02

Starting with the T01-02 13'' spread 12-1 sounded right next to each other but 11-12 sounded like there was a large amount of separation. Where in the T03-02 10-11 sounded right next to each other. 12-2 also sounded on top of each other. Each group had its separations but it seems that the closer the mics are together the better the localization of each sound.

The next two are:

13''spread ORTF Em 158 mics baffle and 21'' spread ORTF Em 158 mics baffle

T01-03 and T03-03

The most interesting group was the last only becaule it was different from the first two. As I started with the T01-03 the degree of 10-12 sounded right next to each other as well as the 12-2. It seems that this was the worst test for localization. It was hard to distinguish between the degrees of 10 and 12, also 12 and 2. Then I shifted gears and listened to the T 03-03. The further the spread in teh ORTF baffle the better the separation of the sound. The localizaton was much better and much more clear. In conclusion the further the mic the better the localization in the ORTF.

Conclulion:

If I could pic one mic out of the six for localization it would be the 21'' spread ORTF Em 158 mics baffle. If I could pic a second runner up it would be the 13'' spread side facing capsules w/baffle Em 158. I found it weird that the closer the side facing baffle the better the sound quality and the further apart the ORTF the better the sound quality.

Depth Perception and the wave

Mike Jorgenson

I tried to do a little analysis of the frequencies in the waveforms in relationship to the sense of percieved distance/depth in the recording. First, a few disclaimers. 1) I'm not 100% sure I'm analyzing the frequencies right. 2) The sounds I've chosen are based on what I feel to be good (or poor also) examples of depth. That said, here we go.
I looked at the frequencies using the spectral frequency view in Adobe Audition. I took tests 03-01, 03-14, 08-3, and 10-11 to try to compare a few things. First, I took test 03-01 and 03-14. These clips are from the same test and the particular clicks I compared are the same click. In addition, I chose 03-14 because it's position was not too far off of the 03-01 position. So, in theory they should sound generally the same. However, they are from different rigs. I found a few things. First, I thought in general the 03-01 sounded like there was a little more distance to the clicks. From just hearing it I thought that one of the major differences was the middle and background noise that affected this depth perception. It seems that the brighter the middle and background tones the closer the object is perceived to be. Comparing the two waveforms this seemed to be confirmed. (This sound is the 03-01 rig click 2x, followed by the 03-14 rig click 2x). The 03-14 rig has much more green and orange in this picture, signifying higher energy sound, in the 4k-10k frequency range. In comparison to the other tests I looked at it seems that the tests that sounded closer (08-03 and 10-11) had more frequency response in this same range. The lower frequencies seemed to roll off in the decay whereas in the 03 tests they did not. They seemed to remain consistent from about 6khz down. In the 08 and 10 tests you can visually see this as the green dissipates bulges in the middle (looking vertically at the click) and then sucks in at the lower frequencies. However, there is also something else to it. Looking horizontally across a small range of frequencies (say roughly one 'spike' horizontally) there are different shapes produced by the high energy and low energy colors through the decay. For example, the 03-01 test has a fat, thin base on the left that spikes fairly quickly (see pic). Test 08-03 has a more bulbous base with only a small spike. And test 10-11 has a fairly consistent slope to it. I viewed test 08-03 as having better depth percieved than test 10-11 and worse then 03-01. So it seems that the more gradual the slope of the energy, the closer the sound appears to be.
The rigs that I have chosen to look at actually says something about this I think. Test 03-01 is one of the tests on the dowel with only a simple baffle. Test 08-03 is a double boundary. Test 10-11 is a triple boundary. It seems that the more boundaries you have, the closer the sound is percieved to be at. Like I said though, I'm no expert. But this is what I found to be true.

Stereo vs. Mono. Is it worth it? By Anna Krutzik

For my test of different variables I chose to see if I could hear any difference between the three tests I had chosen as a good representation of stereo when I put them in mono. To my ears, all of the original tests sounded basically the same, with only very minimal variations on each other. While I could hear the stereo effects in the localization of the dings, not much else seemed to really make it "stereo" sounding. And the dings were sort of tempermental, you could tell the direction of some, but not completely all of them.

So, to test my ears, I compared the same tests in both stereo and mono and noticed an immediate difference between the two. In creating a sense of space, the stereo versions win hands down, the mono versions sounding flat in comparison. Of course, hearing the sound surrounding your ears (in stereo) rather than being duplicated into both ears the same (in mono) creates the feeling of actually standing in the room because it mirrors how a person would actually hear, each ear picking up on different sounds based on their positioning and putting them together to create a composite of the space.

As for the localization of the dings in mono vs. stereo, I didn't hear as much of a difference as I would have expected. For whatever reason, I could consistently hear more difference in the location of the dings between 1-4 in the stereo recording. I'm not quite sure if this is my own mind just subconsciously interperating the difference between hearing the dings from the left to the right side as thinking that the right side dings are more localized. Or if there is a specific technical reason for this. So in the mono versions of the tests, I didn't notice that much of a difference in hearing the dings on the left side.

I thought that maybe listening to the recordings in mono but still viewing the animations which illustrate where the ding is coming from in the clock positioning would fool my mind into thinking that I heard it the same as in stereo. And while it did a little bit, there was still an obvious difference when watching the animation and listening to the stereo version.

All in all, I now appreciate much more fully the value of stereo sound recordings and their ability to recreate and place the listener in the space of the original recording.

I recommend listening to the mono versions first and then to their stereo counterparts immediately after to get the full effect that the stereo brings.

Mono Versions
T4-07
T6-04
T9-02

Stereo Versions
T4-07
T6-04
T9-02

Holly Moore: A Few of My Favorite Things

T3-7

The localization exhibited in the parallel boundary rig is crisp and distinct. When compared to other rigs and positions in the same test, such as position 3 using a front-facing rig with 21" spread and baffle, this one clearly illustrates where the sounds are projected from. It is extremely difficult to distinguish the directional value of the sounds with the baffle in the third position. The 8,9,3,4 positions clearly reveal the area in which they are coming. The distinct reverberations of the dings clarify their position in the space while positions 10,11,12,1,2 highlight the clarity of the EM158 mics without clearly distinguishing the direction in which the sounds are coming.

The difference in depth between the 8,9,3,4 positions compared to the 10,11,12,1,2 positions is great. When used on a parallel boundary rig, these mics impressively exemplify depth within the space. This rig differenciates the closeness of positions 10,11,12,1,2 to the distance of positions 8,9,3,4 much more than the second rig I chose, the pseudo SASS flush mounted with the same 3" inset. The depth is not greater than the triple boundary rigs such as the 6" separated triple boundary rig at position 11.

The architechtural value of this rig is not as great as my other two picks. There is a small amount of displace in the sounds, but it fails to clearly differentiate the open space used to test the rigs.

T4-1

I found the pseudo SASS in the first position to be incredibly clear and crisp with every ding in each direction. This clarity, however, becomes problematic when judging its localization because the sounds tend to overlap in all positions making it difficult to differentiate the direction in which the ding is coming. Each ding appears very close to the position of the rig, causing problems with depth as well. There is greater depth between positions 11 and 1-4, however. The offset of the positioning highlights the architechtural value of the space.

The pseudo SASS offers great architectural value to the open space in which this test took place. The echo provided with the greater distance of the dings in the latter positions sheds light on the proximity of the walls according to the first position of the rig. The tapering off of the dings is a great effect for spacial recording.

T8-4

This rig and EM158 mics, boundary 160 degree rear facing with 2.5" inset and 11" separation, was not my initial pick, but grew on me upon further listening. I came to the conclusion that this rig highlights localization, depth and architectural value more than my other two picks. When comparing this with the other two, this set up promotes the area in which the dings are occurring while pronouncing spacial value with its greater depth. There is a minute echo at each position, which exposes the warehouse space used. The area is slightly flattened by the other rig set ups while the direction of the dings is less obvious than the fourth position boundary rig.

Andy Chaney, Pieper Final Post

note:all recordings have been slowed down to 5% of their original speed

What Rob and myself talked about in terms of what to do for the final analysis revolved around the fact that I had to slow down all of the recordings so that I could hear them (I'm hearing impaired, mostly in the high frequencies). What this did, then, was created some interesting conditions in the sound recordings, such as the large amounts of sustain, which I gauged to be the most accurate aspect of what kind of space was coming across in the recording. Thus, Rob suggested to do a test with several sonograms of the same ding but from different positions, in order to sort of study the waveform and types of frequences each rig was picking up, as well as looking at how each frequency sustained with the rig. Below, you can see three of the tests that I thought really had a nice amount of sustain, which was test 3. I chose station 3 (my own), 7, and 10, and did sonograms on those stations. If you look below, you can see each rig, and the resulting sonogram that each had, as well as listening to the recording, too.

Picture of Test 3, Station 3 Rig compared against the Sonogram For Test 3, Station 3. 12 O'Clock Ding.



















Listen to the slowed down recording of Test 3, Station 3
(Click on "download full URL" to download the mp4 file)


Picture of the Test 3, Station 7 rig, compared to the Sonogram for Test 3, Station 7. 12 O'Clock





















Listen to the slowed down recording from Test 3, station 7


Picture of the Test 3, Station 10 Rig compared to the Sonogram for Test 3, Station 10, 12 O'Clock Ding



























Listen to the slowed down recording from Test 3, Station 10

Results:
Where this test seems to hold the most promise is in terms of how the rigs performed according to what they were showing in terms of the frequency response. A quick note about the sonograms: what they represent is each frequency, high and low, and how long they were still showing a response. The higher up on the chart, the higher the frequency, as you can see on the sonograms. In terms of the results of this test, #3 and #7 performed much better than #10 did. As you can see on the sonogram above, #3 and #7 had very good responses across all of the frequencies, and they seemed to sustain much better, judging by the longer responses than on #10. #10 had very "thin" responses even in the initial part of the sonogram, I don't know if this meant that the sounds were not picked up very well by the microphone, but looking at the sonogram, they don't seem as strong as the ones in #3 and #7. I noticed that in #3, some of the mid-frequencies seemed to hold almost until the end, and the higher frequencies had a nice response. This sort of feels consistent with my initial observations about why I liked those recordings in the first place, because of the interesting sustain that they captured. I described it as feeling as if the sounds were being held by the microphone and the rig even after the initial sounds had passed. It gave the room a weird localization. #7 had similar characteristics in its sonogram as #3 did, although the sonogram got cut off a little bit at the end during the transfer process to blogger. #10 just didn't seem to sustain as well as the other ones did, and perhaps that was indicative of the rig type, where the other two were parallel boundaries and probably had a little bit of the sound being contained, or bouncing off the rigs, #10 did not have the same rig characteristics, and that seems to be reflected in the test. Also, I didn't notice any specific variations in this test because of it, but I intentionally chose ones that had a baffle, or that didn't have a baffle, so that I could contrast the parallel boundary sonograms with a baffle, and a parallel boundary without a baffle, etc. And then a rig without the parallel boundary, but with a baffle. However, I couldn't really discern any specific results in terms of the baffle or no baffle, I thought it might show a different type of frequency sustain, but it wasn't really reflected in the test.