(audio only) gunfire

[cam235]

(EDIT) Unfortunately there was a local shooting last night. I don't know if an audio-only recording from about 1/2 mile away tells much, but what was reported on Nextdoor from more immediate neighbors was 5 shots. From this audio, it sounds a lot like there were a few additional shots (muffled and with an echo), possibly from a different angle or more enclosed position, about 5 seconds before that (?)

 

[looney2ns]

From reports, unfortunately there was a homicide last night. I don't know if an audio-only recording from about 1/2 mile away tells much, but what was reported on Nextdoor from more immediate neighbors was 5 shots. From this audio, it sounds a lot like there were a few additional shots (muffled and with an echo), possibly from a different angle or more enclosed position, about 5 seconds before that (?)

Or two different shooters. What did you capture that with?

 

[cam235]

I have tried a few different external mics, and the Dahua turret internal mics are not bad, but I still wasn't satisfied with the noise level. That recording is a home-brew custom mic which picks up faint sounds somewhat better. Partly due to a low-noise electret capsule (spec is 80 dB SNR http://www.puiaudio.com/pdf/AOM-5024L-HD-R.pdf ) and a low-noise preamp, I had to add extra noise filtering on the power supply to the preamp, otherwise it picked up digital buzzy noises. That goes through a Behringer Line2USB cable and into a mini-PC which records audio as MP3 files 24/7. The mic is mounted under the eaves right in a corner formed by the wall, roof and supporting beam which makes it somewhat directional, towards the incident in this case. I used a long USB extension/repeater cable to the miniPC in a separate enclosure, also containing a router for various cameras.

 

[Frankydp]

To me. Sounds like 2 shots inside something, vehicle maybe, then a car crash of some kind then the 5 follow on shots.

What are you using to record on the mini-PC?

 

[cam235]

If the news report is right, the first shots were into the car after it crashed, and the second set was at a fleeing passenger. (EDIT) Another news source said car was shot at, then crashed into parked cars + tree so you may be exactly right.

As for recording software, I'm running Linux using a command-line program, ffmpeg set to record 5-minute long files (300 seconds) continually, with time & date in the filename like this:

ffmpeg -f alsa -ac 2 -ar 48000 -i plughw:0 -map 0:0 -acodec libmp3lame \
-b:a 192k -f segment -strftime 1 -segment_time 300 -segment_atclocktime 1 \
/audio/ChA_%Y-%m-%d_%H-%M-%S.mp3

 

[J Sigmo]

We have so much wind here, that often the audio from my cameras is overwhelmed by the effect of the air rushing over the microphone openings. I have added some very crude wind abatement, but I may well install a separate microphone with a proper "dead cat" over it to see if I can get more wind resistance that way. But there may be nothing that will effectively deal with the frequent 70+ MPH gusts we have here in the winter months.

Your audio is very clear. Well done on the setup!

I do find the audio from my outdoor cameras to be quite informative and interesting. Surprisingly so!

 

[cam235]

Thanks for the comment. I doubt this would work in 70 mph wind. So far, so good with the mild weather here. I was worried about humidity so I sealed the mic element (in a short tube), into a 4-mil latex "finger cot" with a packet of silica gel. Then the mic assembly was built into a semicircular corner section made of thin wood sheet, covered with a piece of nylon stocking which is trapping about 2" of dead air space in front of the mic, all this mounted in a corner under the eaves of the house. Close up it's hideously ugly, but after painting some cardboard crudely mounted up flush to the mic edge, it may be mistaken for part of the house structure. From a distance, it's hard to see.
When the community service officer came to collect this recording, they wanted to see the mic, but had no further comment after seeing it, I don't know what they were thinking!


EDIT: today there is a slight wind going to 15 mph, and the background noise goes way up. Not because of direct wind on the mic, but from rustling leaves on several trees nearby. The original recording was in pretty much still conditions.

 

[tangent]

it probably took a fairly serious incident to get you to create this mic.

 

[cam235]

as you guessed, this wasn't the first shooting in the area.

 

[J Sigmo]

Thanks for the comment. I doubt this would work in 70 mph wind. So far, so good with the mild weather here. I was worried about humidity so I sealed the mic element (in a short tube), into a 4-mil latex "finger cot" with a packet of silica gel. Then the mic assembly was built into a semicircular corner section made of thin wood sheet, covered with a piece of nylon stocking which is trapping about 2" of dead air space in front of the mic, all this mounted in a corner under the eaves of the house. Close up it's hideously ugly, but after painting some cardboard crudely mounted up flush to the mic edge, it may be mistaken for part of the house structure. From a distance, it's hard to see.
When the community service officer came to collect this recording, they wanted to see the mic, but had no further comment after seeing it, I don't know what they were thinking!
View attachment 26497 View attachment 26498

EDIT: today there is a slight wind going to 15 mph, and the background noise goes way up. Not because of direct wind on the mic, but from rustling leaves on several trees nearby. The original recording was in pretty much still conditions.

That's a nice setup! It doesn't have to look pretty if it works well!

Yeah, even without the direct mic problems from wind, you certainly do get a lot of added noise from wind acting on anything in the area. When it's calm here, I'm amazed at what I can hear from my security cameras. When it's windy (and that's a lot of the time here), it really makes a lot of noise.

It's calm here right now. I'm sitting here at my PC surfing this forum, and listening to a lot of birds chirping and the noise of cars driving past with the BI screen up on the 2nd monitor on this PC. Darn, cars are noisy! You can hear them from blocks away - just the noise of the tires on the pavement, mostly.

I've twice had cars hit-and-run my vehicles parked on the street. I think the sounds would be a valuable added stream of information in a capture of such an event. People drive too fast on this street, and it's somewhat narrow for being such a well-used thoroughfare. And, it gets icy a lot. That makes it pretty easy for accidents to happen. It'd just be nice to get THEIR insurance (if they have any) to pay the next time!

Man, that guy that just drove by needs to check his water pump ASAP!

 

[cam235]

Yeah, sound definitely tells you something. Here's a random car from 3am this morning- just some guy doing 50 on our narrow 25-mph side street. I'm surprised he didn't hit anything. Discovered this morning the one camera set up for cars at night had the illuminator power supply fail. Not much detail on the other cameras, but the audio comes through OK!