Longest Sound File?
November 15, 2007 7:13 PM   Subscribe

What is the duration of the longest digital (or digitized) sound recording? What is it of? And where can it be listened to? I'm not interested in midi, only natural recorded sound. Is there a theoretical limit to a digital sound recording? Tape can go on forever, but filesystems and drive space would have to eventually limit the size of the file (or do I have that wrong?). Just curious. I'll take my answer off the air.
posted by cjorgensen to Technology (12 answers total) 5 users marked this as a favorite
On a modern hard drive, you could store a couple years' worth of recorded sound, depending on the compression used. With hot pluggable hard drives, you could easily make a system that continuously records sound for as long as the hardware stays in working order.

As to if anyone has done such a thing: ECHELON.
posted by demiurge at 7:24 PM on November 15, 2007

Indeed, the storage medium would restrict its length. That is the only theoretical time limit. That, and the working memory cache of the program recording the sound. But a few other factors play large parts in this restriction, such as its file type/compression and quality.

For example, an uncompressed .wav file might take up 50 times the hard drive space than a 92kbps mp3.
posted by blastrid at 7:32 PM on November 15, 2007

According to the handy A-NO-NE DAW Disk Space Calculator dashboard widget, 40 hours of a terrible quality 8 bit 8k sample rate recording would take up approximately 1 gig.

So, multiply that times however many gigs you have. It comes out to around 4.5 years of recording for a terabyte hard drive. That is, except for file size limitations (I'm not sure what those would be).

A more decent 16 bit, 44.1k sample rate recording would clock in at between 3 and 4 hours per gig for one track. 145 days per terabyte.
posted by umbú at 7:37 PM on November 15, 2007

There are probably lots of continuous recorders running right now, all around the world, just digitizing sounds and recording them to some medium without stopping (just as an example, most radio stations have recorders that monitor everything that's broadcast, and a station that broadcasts 24/7 assumedly has recorders running continuously as well, although it probably gets broken into chunks periodically for storage).

Really what you'd be asking is "what's the longest-running continuous digital recording," since I'm nearly positive that the front-runner is going to be something that's in-progress right now.

I don't have an answer for you, and a lot depends on how you define the particulars of the question (does it all have to be in one file? how about one file broken across multiple logical partitions? multiple physical storage units? a SAN?), but I suspect if you are loose enough with "sound file" there are probably stations that have digital recordings going continuously for years.
posted by Kadin2048 at 7:44 PM on November 15, 2007

cjorgensen posted "Tape can go on forever, but filesystems and drive space would have to eventually limit the size of the file (or do I have that wrong?)."

Modern server architecture allows for essentially unlimited drive size from the user's point of view. I've worked at a place with over a petabyte online, all under a single drive letter. Streaming technology allows for multiple files to appear to be one big file to the listener.

As to the longest duration sound recording; I'd imagine someone is recording the output from the longplayer project which has been playing for 7 years now and is planned for a 1000 in total.
posted by Mitheral at 7:56 PM on November 15, 2007

Don't know if it answers your question but there does exist a 1000 year long piece of music.
posted by mmascolino at 7:58 PM on November 15, 2007

Drats...beat me to it.
posted by mmascolino at 7:59 PM on November 15, 2007

If the OP's question is (as I read it) what the longest-duration SINGLE audio file could be using any currently existing tech, the answer would just be mathematical in two parts:

1) what is the lowest bitrate at which it's possible to store audio?

2) what is the largest filesize limitation in any existing OS that can store audio at that bitrate and in that format?

Divide the answer to 2 by the answer to 1 and you get a theoretical longest duration.
posted by allterrainbrain at 9:07 PM on November 15, 2007

I don't know why you say "tape can go one forever" but digital audio can be recorded on tape so if analog can go on "forever," so can digital.
posted by timeistight at 9:30 PM on November 15, 2007

ZFS tops out at an unremarkable 16EB per filesystem/file, so at uncompressed CD quality that's:

(16 exabytes) / (1 411 (kilobits per second)) = 3,236,592.68 years

A voice-specific codec like Speex can in a pinch fit in under 5kbps:

(16 exabytes) / (5 (kilobits per second)) = 913,366,455 years

Of course to store all this you're looking at about 30 million 1TB hard disks, but you don't need all that right now, and I'm sure we'll have slightly bigger drives in a million years or so. You also want to save some space for the metadata, and ZFS's block allocator can get pretty slow when you're approaching capacity, so you want to drop off maybe 20-30% from these estimates.

If you need more space, you could bypass the ZFS filesystem layer and use a ZFS volume pool directly, giving you:

((2^18) exabytes) / (1 411 (kilobits per second)) = 5.30283345 × 1010 years

Roughly 53 billion years, uncompressed. Plenty of time to learn how to dismantle gas giants and turn them into hard disks, power stations, heat sinks and sysadmins.
posted by Freaky at 4:35 AM on November 16, 2007 [4 favorites]

Response by poster: Wow, the longplayer idea is cool. They talk about how soothing it is, but was actually making me a bit anxious to listen to, but relaxation tapes do that to me too. Birdsong and ocean waves were never meant to have narration.

The longplayer thing isn't really a recording though, it's being generated by computers in real time. I'd be more interested in the idea of having the 1000 year record of this when it's done (I'll wait).

I was wondering if recording something like this was even possible.

I was also wondering if there were already any multi-year recordings in existence. Radio stations don't really count, since I was wanting a publicly accessible one.

And bitrate and such, I would hope it would be listenable, and preferably in a format that is portable.
posted by cjorgensen at 6:25 AM on November 16, 2007

I work at a radio station where we have the capacity to record about 7 years of audio at CD quality. We use it for storing ripped albums though. Right now I've set up a system to hold on to the last two weeks of audio, but we could set it to hold on to half a decade with a quick parameter change.

My university also has a a system that records about 12 days of about 4 dozen television channels. Some commerical companies archive far more.

I'd bet the longest recording would be NASA archives of telemetry data from something like Voyager or long term weather research sattelites.

By the way, tape has much more restrictive limitations on maximum recording length than digital audio. Digital audio can scale as long as you keep adding drives, tape will eventually grow too big for the reel to hold it.
posted by phrontist at 8:10 AM on November 16, 2007

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