Field recording

[tristan_louth_robins]

@brasslens

As Coronavirus has caused a total collapse (temporarily, hopefully) in trade for me and my wife we have been going out walking on the Moors near where we live in rural Northern England. The noticeable silence really struck me yesterday. No aeroplanes - normally the bane of my field recording attempts. We are not on any main flight paths but there’s usually a distant drone high up when I want to record something. Looks like I have time and the opportunity to make some rural field recordings! Stay safe everyone.

Yes, this is an unprecedented - extraordinary - time for acoustic ecologies; especially those situated in and around urban environments. R Murray Schaefer’s Utopian visions from the 1970’s (which were covered in detail in his seminal tome, The Soundscape) have been on my mind an awful lot this week. On the absence of planes, this is one of the most striking things I’ve noticed over the past couple of days.

Here in Adelaide, I live in a suburb just to the south of the CBD. The CBD is fenced in my a boundary of sizable parklands and reserves. Much like yourself, we are not under direct flight paths but the sound of planes (especially in the morning) is very noticeable. For the past two days I have heard no planes from early to mid-morning.

Additionally - and this is what’s really blowing my mind - the morning thrum of rush hour traffic is virtually absent, and has been replaced by a striking dynamic equilibrium of sounds - both human-made and natural. In this sense, individual vehicles (heard on our street or nearby) are clearly defined, emerging and then receding into a quiet continuum of wind through trees, birdsong, obscured conversations and an array of indistinguishable sounds. Occasionally, sounds I’ve never heard here before appear; such as a low bell chiming in the far distance. I had no idea what its source was or roughly where it was coming from.

It’s as though an ‘anthropopohonic smog’ has lifted at this moment in time.

Coincidentally enough, I’ve been learning about how to read in and analyse Acoustic Complexity indices in R code (w/ thanks to @zebra who tipped me off on this in the Max/MSP thread!) and I feel this is a great opportunity to make some recordings of my altered urban soundscape for future and comparative analysis. I started this morning by making a recording on our balcony, capturing 15 minutes of a Saturday morning. I may post these to a channel/playlist on Soundcloud/Mixcloud as a series.

Without getting too scientific and dry, there’s also a profound poetic quality to this phenomenon as well, so I’m keen to formulate these ideas, rumination and observations at some point in the near future.

[Shiftr]

Finally got hold of a Sony-A10 for a little bit more reasonable price then i saw before.
Did some quick comparison with my old H1 which it will replace.
The sound is much more neutral and less colored then the zoom. Much more usable.
The self noise seems to be a little bit lower but not that much. The max gain seems to be much higher on the A10.
Also did a quick comparison to it’s bigger brother the D100 and also that didn’t disappoint me.
The A10 got some bad reviews but I think i’ll be happy with it.

This is going to be the recorder that i always carry with me for some time I hope. The Zoom must be maybe 10 years old already. But it started being quirky recently.

[niall]

@Catchthehare

Uši Pros

These look really nice. Does LOM have a presales support email address? I haven’t found one on the site, and my questions aren’t answered by the FAQ.

[edit: it looks like I can “open a ticket” without registering.]

[vehka]

Regarding airplanes, my friend just tipped me off to this amazing album by Rupert Cox and Angus Carlyle, which, well, embraces plane noise. It’s recorded during a fieldwork in a farming community right next to Tokyo’s Narita airport: https://www.gruenrekorder.de/?page_id=8437.

[niall]

Louisville, the city I call home these days, is the base for a lot of logistics companies (UPS’ facility here is called the “Worldhub”); it’s a small city with a lot of freight train lines (which I love, but it’s hard to get a clean recording of them from a distance) and it’s difficult to find a place that’s not under some flight path. I haven’t found public traffic records, but it definitely sounds like there are more cargo planes flying overhead. I spend a few hours a day walking in our lovely city parks, and I’ve heard the roar of aircraft more in the last week or so than previously.

[Pida]

I have two questions.

(1) Can anyone point me to audio recordings that were made at high sample rates and then slowed down to reveal interesting sounds which are normally hidden in inaudible frequencies?

(2) Which portable recorders record at 192 kHz? Is that the maximum sample rate for prosumer devices?

[fourhoarder]

this is somewhat controversial but is supposedly a recording of crickets slowed way down. prob not a high sample rate!

[ermina]

i found a video called " Here’s What Bat Echolocation Sounds Like, Slowed Down" where you have 3 seconds of relevant audio alongside with music and commentary. But you get the idea, any bat detector with sonification will let you hear that.

Search also turn up these slow-motion videos which explicitly state being 96kHz sound slowed-down.

[pleurodesis]

So this all centers around a higher sample rate being able to stretch out with greater fidelity? I don’t need the video part, so could I could probably take a high sample rate recording and slow it down in audacity, no?
I’ve wanted to get a high sample rate device for recording ultrasonics with (bats and so on), so maybe this is a bonus.

[hermbot]

My concern: wouldn’t most recording devices have antialiasing filters to prevent that material from being recorded?

[Pida]

@pleurodesis

So this all centers around a higher sample rate being able to stretch out with greater fidelity? I don’t need the video part, so could I could probably take a high sample rate recording and slow it down in audacity, no?
I’ve wanted to get a high sample rate device for recording ultrasonics with (bats and so on), so maybe this is a bonus.

Yeah, this is the kind of application I’m interested in.

@hermbot

My concern: wouldn’t most recording devices have antialiasing filters to prevent that material from being recorded?

That is a great point. Does anyone know anything about devices that can record audio outside the audible range for humans at high sample rates?

I see that the Tascam DR-100mkIII and Sound Devices MixPre (mkII) series both record at 192 kHz, but I don’t know what kind of antialiasing (or other) filters they might have.

[_mark]

If you record at 192khz you will get some sound up to 50-60khz with most microphones. This lets you pitch down further and still retain highs. I’ve never discovered anything new doing this (as in couldn’t be heard before) but it is very worthwhile. You need higher than 192khz for bat’s though.

I’ve been trying to get hold of the 100k sanken mic for a while now. Apparently a game changer for this sort of sound manipulation, but lots of money.

[sam]

@Pida

but I don’t know what kind of antialiasing (or other) filters they might have.

Don’t a lot of ADCs/DACs use delta-sigma to do the actual business to conversion to and from analogue?

So there might be one analogue filter at the delta-sigma stage, possibly quite gentle at a high cutoff, followed by a steep digital filter at the conversion to PCM…

(or am I talking out of my bottom…)

[timp]

Slowing down sounds can reveal character that is less obvious at normal speed, heres a few examples - these are all exterior recordings but eg with the slowed down fireworks you notice the slap/decay from nearby hills more… And modulation of sounds becomes more apparent (eg the cicada which feels more like a tone at normal speed clearly becomes rhythm at 1/8th speed) - these are all recorded with Sennhesier MKH80X0 mics which go 10Hz - 50kHz

[pleurodesis]

Well, macaques are fucking terrifying. That face and that sound together = good lord.
Fascinating though.

[zlp]

Many thanks for the examples, Tim!
Depending on the species, you can get a lot of bat calls with 192kHz (and even 96kHz) rates. I’ve been testing cheap electret capsules to see if they go up to ultrasound frequencies. (Many do.)
https://www.zachpoff.com/resources/cheap-microphones-for-ultrasound/
I just built a better test setup for repeatable measurements, but the COVID situation means I can’t get into work to calibrate it, so it’s on hold for a bit.

This is a quick white noise test of the SD MixPre-6 at 192kHz. Looks like the -3dB point is around 65kHz. I also tested a Focusrite Scarlet 2i2 (Gen2) and cheap Behringer UMC204HD interface: They were -3dB at 45-50kHz. So there’s plenty going on up there!

[zebra]

@sam

Don’t a lot of ADCs/DACs use delta-sigma to do the actual business to conversion to and from analogue?

yep. and these days these are mostly high-order (“multi-level”) sigma-delta architectures.

so the input is sampled at an exremely high rate, but basically at 1-bit (or more) resolution, and then successive stages of decimation filter and noise shaping are applied.

@hermbot

My concern: wouldn’t most recording devices have antialiasing filters to prevent that material from being recorded?

nah, if an ADC supports 192k then decimation passband should go up to 96k.

example:

CS5368_F5.pdf

in a really fast search i could not find a good functional diagram for a high-order sigma-delta ADC. but here’s one for a DAC which shows the same idea in reverse:

https://www.ti.com/lit/ds/symlink/pcm1608.pdf

anyways the takeaway is that if a capture card supports 192k i would consider it a severe case of false advertising if it was just upsampling something with a narrower bandwidth.

[slowsounds]

I know it has been posted on here before, but specifically for ultrasonics it seems like the AudioMoth is probably the cheapest way to get into recording those since it has a build in MEMS- https://www.openacousticdevices.info/. there is also a miniature version in development which I’d def like to try once it is available.

[pleurodesis]

I’ve looked at those since they started the first line. might could set one up on my roof to catch a listen to these Fledermäusen. Hopefully they come out with a good housing for the smaller version since it seems like it took a bit to produce a solution for the normal sized ones; people were DIY’ing all kind of things to put them in.

[zlp]

One thing to keep in mind is that they’re mono-only and quite hissy. (I don’t have hands-on experience but I’ve heard recordings and discussed it with owners.) Awesome machines, though, especially for researchers who have been limited to eye-wateringly expensive options until now!