Congratulations to Mr. and Mrs. Clayton Bloch!

Clayton Bloch and Mary Jane Cochran were married about 2pm at Artillery park in New Orleans on Saturday, May 11, 2013.

a practical example of wavelength

This is a screen capture of an electronic / acoustical signals measurement program called SMAART, which stands for System Measurement Acoustic Analysis Real Time (Tool).  SMAART has a long history of being used in the live sound field to perform system measurements.  In this case, I'm measuring the arrival time between two microphones, an audix tr40 omni measurement microphone, and an Audio Technica 4050 large (ish) diaghram condenser with the low cut off, the pad in, and the pattern set to cardioid.

So what's going on?  Good question!  I'm glad you asked.  What do these squiggly lines mean?

Briefly:
The top window is called the live impulse response.  It basically shows the difference in arrival times between two sources that have the same content (think pink noise coming from a front fill and the Left array)  This is useful for looking at timing data between zones and also polarity (does the waveform increase in amplitude when combined or decrease?).   For this measurement we would actually use 1 measurement signal and a reference signal because we need to know exactly what signal is being supplied (the reference) and is not that useful unless we were comparing two identical mic's.

The middle window is the phase trace:
What is the difference in degree radians (how early or late is a waveform at any given frequency when comparing two sources)? In our case, what is the difference in arrival times between our two microphones.  This would obviously work perfectly if we had perfectly matched microphones, but well, this is the real world, the data is a little messy, and these are the mics I had on stands at the time :)

So, in this case the phase correlates (is the same) pretty much up till we get to 5k, and then there is a slight shift downwards, which would mean that the mic capsule for the 4050 is more sensitive to the higher frequencies, or the frequencies arrived at the 2nd microphone slightly sooner. It looks to me from the phase trace that the largest downward slope is at about 10k.  so what is the wavelength of 10,000 hz?  wavelength = 1127/10000, or about .11 feet, if we were to convert to inches would be .......1.32 inches!  Which is about the difference between the two mic capsules in space!

The third window is the magnitude response:
This is simply a measurement of amplitude difference at any frequency.  The red is a coherence trace, which is an indication of how certain are we that we are getting good data at any given frequencies.  So on this magnitude response, we are comparing the frequency response of the 4050 to the measurement mic (tr40).  It seems like we are getting a relatively flat frequency response up to the upper midrange, and then well, the differences in microphone capsules become apparent, but the upper sub, lows, low mid's, and mid range seem to correlate pretty well.


A couple of formulas to know:

wavelength = speed of sound / frequency

speed of sound = 1127 ft / sec

frequency = 1 / period (time it takes for 1 wave to 1 to travel 1 wavelength)

100 hz's wavelength = 11.3 feet  (I use rounding)

11.3 feet =  1127 feet ( speed of sound) / 100 hz

1000 hz's wavelength =

1.13 feet = 1127 / 1000 hz (1Khz)

I hope this was informative, if anyone has any questions, comments, or corrections, please let me know.



http://en.wikipedia.org/wiki/Wavelength

Hello, World.

Sorry, I know it's been a while.  I've been doing some fun gigs lately, and haven't had the inclination to post.  This is a picture of me wearing a headset to communicate with the crew during a corporate show.

Producing audio for live webcast at Voodoo Music Experience

Transitions

The last few days I've been thinking a lot about transitions. Maybe it's the weather and the empirical changes that Fall brings, but transitions have been on my mind. For instance today, I worked from  home.  Usually I spend forty-five minutes driving to Covington, Louisiana most of it lost in thought while I pass over the most beautiful lake I have ever known.  Thinking about my to do list at work, thinking about house issues I need to tackle that evening, phone calls to make, people to visit, recipes I want to try, etc. But today I was at home. I did not have that time of contemplation. Instead, I woke up a little later, walked Molly and Prudence, did 20 minutes of yoga and met with a carpenter. 

Moreover, what is strange is I was aware when speaking with the carpenter how different today was and how quickly my day was going to change.  And it was not going to change in hours, it was changing now. I was thinking, "In about 30 minutes I have to transition from being a homeowner who wants renovations to a paralegal who needs to make phone calls to set up depositions and review some cases."  And I thought some more, "That's a pretty big change. I am thinking this way now and then pretty quickly I have to start thinking and acting another way."  Then it occurred to me, that such changes in thought and in actions, are pretty difficult. It takes a lot of effort to force your mind somewhere else, to make your body do these movements now!  But why is it so hard?  And if you are not aware of these transitions, can you really shift and still be in the moment? It's amazing to me how each day is different, each hour, each minute.  But then again, maybe it's not. Maybe it's just my perception. (See there's a reason, Chris put "and the philosophy of things in our blog.")  

Of course it could all be in my mind. In fact, as I write this post, my mind is already beginning to shift, to move onto something else. Future blog posts about possible worlds, about Plato, about Molly and Prudence chasing a frog in the park. Time for me to move on.