In the post from June 13th I shared a faint howl that I recorded on the evening of June 12th. The recorder actually intercepted the howl twice, but it was so distant that it wasn't worth sharing both snippets.
But as evidenced in the last few posts, I've been playing around with presentation in the form of spectrogram videos. And I wanted to see just how far I could take it to demonstrate their ability to help audiophiles study sound (and interested onlookers to get more out of the experience).
So this evening I sat down and pulled out the original recording of that faint, distant, flat howl I recorded on June 12th, at 11:13 PM. I applied some heavy filtering to the recording which basically wiped all sound above and below the howl (this worked because the howl was so flat in nature). Then I did the usual noise filtering and amplification, and was very pleasantly surprised by the results. Even listening to it on my laptop speakers, it sounds like a pretty good recording of a howl.
So I took it the next step and played it through my spectrogram software, Sonic Visualiser. As I did so I used "RecordMyDesktop" to make a short video of the spectrogram in action. I loaded that video into PiTiVi, a video editor, and then added my newly cleaned up audio snippet as the sound track. A little tweaking and I had a video ready for loading to Youtube. Here's the result, the brightest parts of the horizontal band of color represents the howl:
But what caught my attention after replaying that howl about 40 times this evening, was a moment when I happened to play another of the Youtube spectrogram videos I've made. That video has a nearly identical howl in it, only captured a few weeks later at sunset on July 2nd. You can see and hear that howl at the 12 second mark in this video:
It comes in apparent response to my whoop and wood knock and before several loud wood knocks toward the end of the recording. It too seems to center around 490Hz and has a basic flat form.
This makes three times that I've recorded this type of howl in my area of investigation. And I hadn't recognized it until I began playing clips and spectrograms from different dates side by side. Obviously my ears and eyes will be much more tuned to that frequency in the future.