1. Audio Formats: Care and Handling
Digital Stewardship Curriculum
Right now, I am just going to give a quick overview of Audio Formats, and some basic information about how to care for them.

2. What kind of audio formats are in your collection?
What media types do you have experience with?
So just before we get started, it would be great to share a bit about your own institutions.

3. Analog Audio Formats Magnetic Audiotape Grooved Media Optical Media
Cassettes,Open Reel
Grooved Media
Records, Wax Cylinders
Optical Media
CDs
When talking about audio, there are four main formats, Magnetic, Grooved, Optical, and Digital.
They each have their own unique care requirements.
We will touch on them all briefly
All images from PSAP

4. Magnetic Media
Open reel, Cassettes, Digital Audio Tape, Wire Recordings
Composed of a base, binder and metal particles that hold the sound recording
First, Magnetic Media.
Most common is your regular old cassette tape. But there are also older formats like open reel and wire recordings.
Except for wire recordings, these are all composed of some kind of tough base tape, and then metal flakes or particles adhered to the base.
Those metal flakes are magnetized and that is what captures the recording.
In the case of wire, the entire wire is magnetized.

5. Here we have and Open Reel, or Reel-to-Reel recording on the left,
And a Cassette tape on the right.
In principle they are very similar! The open reel is just bigger and… open, so it’s more delicate.
Can you note anything (problematic) with the open reel?

6. Up on the left here is Wire spool recording (side view)
Up on the left here is Wire spool recording (side view). These are pretty rare.
I haven’t even seen what a player looks like and frankly wouldn’t know the first thing about working with them!
Except I know that they get VERY tangled. If you have wire recordings, find a professional to help you!
Image by Flickr user Betsian, available under a Creative Commons Attribution-NonCommerical-ShareAlike license (CC BY-NC-SA 2.0)
And on the right are DAT cassettes. DAT stands for digital audio tape.
On the technical level they function more like a VHS cassette than anything else.
They’re about half the size of a regular audio cassette.
Image by Lori Dedeyan, available under a Creative Commons Attribution-NonCommercial-ShareAlike license (CC BY-NC-SA 2.0). Courtesy of UCLA Library Special Collections.

7. Magnetic Media Preservation
Lack of (working) playback equipment
Brittleness, physical damage
Demagnetization over time
Mold
Substrate and recording media delamination
I want to say that I’m always surprised at just how durable regular audio cassettes are.
The biggest problem is getting the equipment to work with them.
Really only one company manufactures a decent consumer-grade tape deck these days. And finding spare parts or a qualified technician is even harder - so now is kind of a crucial time to digitize audio tapes!
Some of the common preservation concerns around magnetic media are actually pretty easy to deal with.
Keep things cool, dark, and dry, and handle carefully.
Some materials may start to delaminate or suffer other damage, but if you’re careful and thoughtful, you can actually store these things pretty easily.

8. Grooved Media Wax Cylinders Discs Vinyl Shellac
Acetate (metal or glass)
Next, grooved media!
Most likely we are all pretty familiar with vinyl records - LPs, EPs, 33s, 45s, etc…
That same format was also made out of shellac, metal and glass.
And there are also wax cylinder recordings which are older. They’re pretty neat, actually, and work basically the same as a record, just top to bottom, instead of outside-in

9. Left is a Vinyl LP (33⅓rpm) record, measuring 12" in diameter
Left is a Vinyl LP (33⅓rpm) record, measuring 12" in diameter. This should be familiar.
Right in an Aluminum disc. Image courtesy of Aaron Coe, The Cutting Corporation.
Same principle, different material.

10. Left are some Cracked and fragmented cylinders
Left are some Cracked and fragmented cylinders. This is a very common sight with wax cylinders.
IRENE
Image by Flickr user Photo Phiend, available under a Creative Commons Attribution-NonCommercial-NoDerivs license (CC BY-NC-ND 2.0). Courtesy of Library of Congress Preservation division.
And on the right, and intact Wax cylinder with original box. Image by Flickr user Marcin Wichary, available under a Creative Commons Attribution license (CC BY 2.0).

11. Grooved Media Preservation
Lack of (working) playback equipment
Playback wears out the recordings
Wax Cylinders
Very fragile
Discs
Fairly fragile
Delamination
Unfortunately, grooved media is a lot more fragile than magnetic media.
Wax cylinders and most record types are prone to cracking or shattering.
Vinyl and shellac records in particular are at risk of delaminating and separating.
Also, since grooved media are played by basically dragging a needle through the grooves, they wear out with use.
In general, keep everything cool, and be careful with handling and storage.

12. Optical Media Minidisc CD Optical media.
These are relatively recent, and the first digital recording media we’re really looking at.

13. These are some shots of a minidisc.
These really did not last long. They were big in Japan, and I had one or two really cool and/or nerdy friends who had them, but they didn’t take off here.

14. The CD, the compact disc.
Light, kind of portable, cheap, generally played nice with computers and replaced the venerable mixtape.
They’re composed of layers of plastic and foil, and read by a laser.
GET THINGS OFF OF THESE, no digitization needed

15. Optical Media Preservation
Lack of (working) playback equipment
Physical damage
Scratching
Corrosion
Delamination
Spontaneous Failure
I, for one, am pretty glad that these media have more or less had their heyday.
Even though there are in theory golden DVDs that can last thousands of years, optical media are volatile. They don’t last and they are prone to spontaneously degrading or losing data.
Pretty standard preservation concerns…. but I say since it’s a digital media and is pretty easy to copy from a disc, get your content off these as soon as you can. They do not last as long as analog media.

16. Care and Handling, Storage of Analog
Don’t touch the recording media
Handle discs by edges
Store in cool, dry, dark place
Handle with clean hands (or gloves)
Store media on-edge/upright
Use acid-free/archival cases to store
Re-house if necessary
Use the right size cases
This is kind of a catch-all summary of the preservation needs for analog audio media.
You have more detailed information in your packets

17. Resources for Identification
Quick Guide in packets
PSAP
Museum of Obsolete Media
Field Audio Collection Evaluation Tool (FACET)
Library of Congress
Connecting to Collections

18. Analog to Digital Conversion

19. Analog and Digital Signals
An analog signal, like what you hear right now, and what is more or less recorded on tape or vinyl, can be represented as continuous signal.
Here, it’s a simple sine wave. A waveform like these is showing amplitude (basically loudness) over time.
Digital recordings can’t truly capture that continuous, smooth signal, and functionally capture tiny tiny snapshots of the continuous signal.
Don’t worry about it, but the process is called quantization.

20. Analog and Digital Signals
And a sample of human speech.
This is 10 seconds of speech.
There are a lot of very minute bits of data here, which is choosing the right level of detail in your recordings is important - you don’t want to lose information!

21. Analog and Digital Signals
When talking about digitizing audio, we always refer to the Sampling Rate and Bit Depth.
Sampling Rate is the frequency at which “snapshots” are captured per second.
Usually expressed in Hz or kHz - 1 sample per second would be 1 Hz. That would also be useless and your recording wouldn’t sound like… anything at all really.
On the other end, most humans can’t sense anything above 20,000 Hz. But we usually want to capture more than that to be on the safe side - there might be information present that you can’t hear yourself, especially in music, songs, or natural sounds.
Bit Depth is the resolution of the data. More bits means a wider range of information is possible to be captured.
(such an embarrasing site)

22. Analog and Digital Signals
This image shows what happens when you consider Sampling Rate AND Bit Depth.
The takeaway is that the higher the sampling rate and bit depth, the more FAITHFUL and ACCURATE your digital capture will be to the analog original.
The caveat is that a poor recording may not benefit from extremely high level digitization.
[its actually 44.1 khz AND its a holdover from CD mastering days, which is most def out the door as a distribution medium in any case; we are moving to 48khz/16 bit for access copies; moreover, there’s a school of thought that fractional frame rates are unnecessary in the “files only, no carriers, please” age which we are now in\.

23. Digital File Formats
Recommendation Level
File Format
Sample Rate
File Bit-depth
Usage Example
Minimum
WAV/AIFF
44,100 16
Audio from commercial CD
Special Consideration
48,000 24
Human voice only, no instrumental music
Recommended
96,000
Oral History recording, especially if there is music.
Natural sounds or sounds from nature.
Recommendation Level
File Format
Bit Rate
Usage Example
Minimum
MP3
128 Kbps
Oral history, without music
Recommended
192 Kbps
Most audio
Special
320 Kbps
Very high fidelity required
The question always comes up: How good is good enough? Well…
These are fairly well-established standard settings.
Top: Preservation
Bottom: Access
People often abbreviate them, like “Oh yeah, this was recorded at 96/24, but then we downsampled it to 44/16 for the access copy”
Bit rate expresses the number of bits captured per second.
The formula is Sample rate x Bit-depth x Number of Channels
Higher bit-rate = bigger digital file

24. Digital File Formats WAV for Preservation Sample rate: 48 or 96 kHZ
Bit depth: 24 bits
1-2 GB/hr
MP3 for Access
Bit rate: 192 Kbps
86 MB/hr
Again, you have more detailed information in your binders, but as a rule of thumb, use WAV for preservation and mp3 for access files.
This is as close to an industry standard practice as you can find.

25. Digital Storage
3-2-1!
At least 3 copies, on at least 2 different storage media, 1 of which is in a different geographic threat region
Always going back to the rule!