Audio

Preservation

The collection storage room is designed specifically to house our audio and video media. With limited access and specialized shelving, coupled with strict temperature and humidity control, we ensure an ideal environment for the long-term storage of magnetic tape, thereby maximizing the life of the recording medium.

Data

Aside from simply documenting who made a recording, identifying the species, and noting where and when the recording was made, we also store valuable information on the recording equipment used, detailed behavior and habitat descriptions, and weather conditions. We make an effort to supplement information not originally noted by the recordists by consulting experts to note additional information, such as the the call type or identifying other species vocalizing in the background.

Protocols for consistency

Over the years, the Macaulay Library has developed protocols to ensure uniformity in the way each recording is preserved as a 'specimen' and associated data are stored. The goal is, if an archivist from 1960, 2004, or 2040 were to be given the same field recording, all would generate nearly identical specimens. While advances in technology have and will alter and expand the way in which the work is done, the essence of the archived specimen should remain consistent.

Restoration

Over time, problems develop with recording media in both analog and digital formats. For example, tapes may become sticky and/or shed, causing the oxide (material the sound is stored on) to separate from the tape backing, resulting in lost information that can never be reclaimed. Tape stocks may also dry out and become brittle, making playback without damage nearly impossible. We have the expertise and facilities on-site to temporarily correct many of these problems, thereby allowing us to digitize otherwise unplayable recordings.

How does the digital archival process work?

Audio field recordings are put into a digital editing system at sampling rates of either 96 kHz or 192 kHz and a depth of 24 bits, using either Prism Sound or dCS analog to digital converters. While these may seem like extraordinarily high sampling rates for many species, it provides unparalleled fidelity, signal resolution, and the ability to handle many of the ultrasonic signals produced by toothed whales, bats, and other wildlife.

Specimen creation and editing

After putting the raw field recording, the archivist uses standardized protocols for determining where one specimen ends and another begins. Some example criteria used for these decisions are whether the recording equipment was turned off and for how long, or whether the species or the individual of interest during a recording changes. The field material is edited into audio specimens with a powerful digital sound-editing program, SonicStudioHD. After identifying the specimen on the original field recording, the archivist assigns a catalog number, adds a voice announcement of the catalog number, digitizes the desired audio segment, and optimizes the amplitude of the sound of interest. Other than level optimization, archivists strive to maintain the specimen as it came from the field. No additional manipulation of the sound occurs and filtering is used only when the amplitude level setting on a particular sound is challenging due to low-frequency interference, such as from wind or equipment handling.

Data entry

The associated data record for each audio specimen is created by the archivist, mostly from information provided by the recordist. Using the recordist's notes, the archivists enter precise information on time and location, habitat description, behavioral context, equipment setup, and any other information available. Data are stored in a relational database, allowing powerful searches on multiple fields and text entries.

Output

The output of the digitization process is high resolution (96 kHz/24-bit) AIFF audio files, which are written onto two, first-generation DVD-ROM discs. One DVD is stored on-site, and the second serves as a safety copy that is sent to a secure, off-site, climate-controlled facility. The high-resolution files are also down-sampled into more readily accessible and more easily-distributed lower resolution formats such as .wav, .mp3, and QuickTime.

Storage/delivery

Assets are stored on a Apple Xserve/X-RAID array with a 70-terabyte (TB) storage capability. This equates to approximately 25,000 hours of high-resolution monaural audio storage. Lower-resolution files are also stored on this array where they are accessible to staff on an internal network, and the public via our online archive. All lower resolution digital files are backed up in an Exabyte LTO tape library located off-site. New or recently digitized material is accessible to the public shortly after it is archived.

Quality control

Quality control is a critical part of our archival process. Archival studio equipment is frequently calibrated to known International Standards. Internal operating protocols are in place to ensure consistent quality standards, throughout the archival process. Additionally, archivists double-check each others' work after archiving a body of recordings. The storage media (DVDs) are also quality control checked pre- and post-writing. All DVD-Rs are analyzed by using an AudioDev CATS DVD-R/RW Pro audio analyzer system to ensure that they meet or exceed industry standards. Discs that either fail or are of marginal quality are rejected. To monitor the stability and longevity of the digital archive, DVD discs are randomly selected and re-tested. We then compare test data from initial disc creation to current tests, looking for any signs of change or manufacturing batch-related problems.