It is one of the facts about natural sound recording that nothing happens for much of the time. You will still be recording, because your subjects aren't directed like human actors are, and you have to be recording when they decide to make a sound. To keep your listener's interest you need to strip out much of this dead time, and it will save you a lot of storage space and make it easier to find what you want.
In days gone by this process was achived by mechanically cutting sections out of the recording medium and rearranging the running order, or copying the wanted sections onto another recorder. Fortunately you can do that with a sound editor on your PC. Unlike the irreversible cutting of the tape, a sound editor allows you to try an edit, and roll back without loss if it doesn't work out.
If you don't currently have a sound editor, the open source (and free) editor Audacity is a good place to start. It works on the three most popular personal computing operating systems. It is a good editor, with all the features you need for editing. Where Audacity is weak is in the area of resampling, filtering and noise reduction, but this is not a major issue when you are starting out provided you record at 44.1kHz.
Later on if you feel you need these features your can investigate commercial offerings such as Adobe Audition, Sound Forge and others, see links at the botton of this page. Sound recordists do not need the range of features musicians need, and it is worth getting some experience with the free Audacity so you have an understanding of how you use digital audio editing software and what you want of it before investing in a commercial product.
You can change the frequency response of the recording using equalisation and filtering, and many programs claim to offer impressive levels of noise reduction. Modest equalisation can help your recording, and compensate for frequency response anomalies of your microphones. Few birds generate sounds below 300Hz, but the modern world is noisy. Transportation generally creates a low-frequency rumble which will often mar otherwise good recordings, and so reducing frequencies below a few hundred Hz can reduce this unwanted sound without changing your wanted sound. Beware of false promises though - you can only do so much of this before your recording starts to sound very unnatural, as few sources of unwanted noise have the decency to confine themselves entirely to low frequencies. If you do use equalisation or noise reduction, you may wish to consider storing a copy of the unmodified original recording, so that you can perform some kinds of scientific analysis at a later date or revisit your processing decisions in the future.
the first law of signal processing:
Signal quality once lost can never be regained
Despite what is often hoped, you cannot pull a good result from a rotten recording. You can't filter wideband noise like aircraft noise or wind blast out of your recordings. Noise reduction will reduce noise, but will also reduce the quality of the wanted sound.
It is generally better to invest the time and effort in getting a good recording at the start, that to try and push a poor recording by processing to try and fix things later. Wind noise in particular, should be addressed by using better wind protection rather than trying to use low-frequency filtering.
Storage and retrieval
Wildlife recordings are often short clips, and you may want to retrieve them based on species and other criteria. It is worth organising your collection of recordings as you make them, so that you can find them again. Take a look at the submission criteria from the British Library National Sound Archive for a comprehensive list of recording information. At the very least, your system should try and record the following data about the recording:
- Date and time of recording
- recorded event location (country, county,locality,exact location, grid ref)
- clip duration
- microphones and recorder used
- reel/CD number and track number or filename
- compression used if any
- equalisation/postprocessing used
- sampling rate and bit depth
- notes about recording
Desktop Audio Workstation (DAW);
There are a number of DAW applications on the market therse are the most popular with WSRS members.