Microphone design    Home    Analysis software

Record audio and extract calls automatically on PCs (updated July 20, 2019)

COMPUTERS

Recording sound from the night sky directly to computer hard drive is the most efficient way to document avian night flight calling. Ten hours of recording (22050 kHz, 16 bit sampling parameters) translates to ~ 1.6 Gigabytes of hard drive space. Recording directly to a hard drive gives you a digital soundfile that can then be analyzed for bird calls ~50x faster than real time with a moderately powerful PC running Old Bird's automatic detection software. This software can also work in real-time and run through the night depositing short files of potential bird calls in a folder on the computer. The Old Bird call detection software only works on PCs and only on mono, 22050 sampling rate 16 bit resolution wav files.

 

For recording audio on PCs, third party software is available for recording at specific times and automatically naming and saving sound files to a specific folder on your computer. For example,  I-Sound (~ $25 USD). An important consideration for automatic nightly recording is to set up the computer so that in event of a power outage the computer automatically returns to automatic recording status once power returns. To do this one must go into the PC's BIOS and set up automatic bootup after power outage in the Power Management section (this is typically only available on desktop PCs). One must also make sure that the option is selected to have the recording software (e.g. I-Sound) automatically reinitiate after the computer restarts. The software can be set to automatically name the nightly files with the date and time of recording. The Easy H-Q recorder allows one to add a specific text name in addition. This is useful if you have multiple stations and want to also label a recording with a site name. One trick to using both Easy Hi-Q and I-Sound is that once you have selected your settings, you need to quit the program and reboot your computer in order for any settings you specify to carry over if there is power outage. Note also that there is a 2 GB file size limit for wav files - this correspondes to about a 12 hour record time.

 

Most PCs come with a soundcard installed, but there are many different types. Most have a microphone input and a line-level input. If you are running directly from a microphone to the computer, you will want to use the microphone level input. In most cases, the home-built design offered on oldbird.org will need a preamp to boost the signal up to microphone level. It will be important to test the input recording level to make sure it is set at a reasonable level - not too loud or too weak. On most PCs the recording input level adjustment can be set by double clicking the sound level control icon in the lower right of the Start menu bar (little, often gray-colored, megaphone-looking icon). You double click this volume control then select the options pull down menu (upper left on the volume control window). Select properties, then select recording, then select OK (make sure the microphone volume control is selected), and adjust the microphone volume. Many newer computer soundcards have a mic boost option than can be implemented in the volume controls, typically in an advanced controls section (accessible by clicking on options). This increases the loudness of the signal. A caveat is that many newer PCs have soundcards that come off the shelf only supporting a 16 kHz sampling rate, which is not high enough to render many high-pitched night flight calls -- spectrograms will only show sound energy up to about 8 kHz. In some cases you can adjust the computer's soundcard's options to access recording at higher sample rates. Another option is to buy a USB sound card (~ $25 USD) and bypass your computer's sound input. Most USB soundcards support at least a 44.1 kHz sampling rate.

 

You will need some way to assess how loud your input signal is. Audacity is free sound recording software that allows you to see your recording input levels. If you are using the Easy HiQ or I-Sound Recorder, you can simultaneously adjust the microphone input level and see the input sound level vary in the recorder window. For I-Sound, quiet night background noise should show about a quarter of the of way up the signal strength indicator. This allows enough room for bird calls that are louder than the background noise to be recorded without being distorted. Inevitably, the calls of some low flying birds will be too loud and end up being distorted. In most cases these calls can still be classified to species when spectrographically analyzed (e.g., with Old Bird's GlassOFire software). The goal in setting the input recording level is to record the bulk of the calls loud enough for spectrographic analysis but without distortion. You will want to experiment with your input recording levels to find a good setting.

 

In most cases when building your own microphone following the instructions on the microphone construction page, even using the mic boost option on newer sound cards, running the signal from your microphone directly into the microphone input of your computer will produce too weak a signal. You will very likely need a preamp to boost the signal from your microphone before you run the signal into your computer. The USB Dual Pre (~$75 USD; still available as of July 2019) is one that works well with the circuit noted on the microphone construction page. This preamp allows you to turn off its 48V phantom powering and let the 9V battery power the circuit. It also has a second channel to facilitate a stereo monitoring system and can operate on battery power for off-grid operation.

 

Call detector programs such as Tseep-r & Thrush-r can be run similtaneously as all-night recording programs like I-Sound. This does not use much hard drive space and this type of call detection can be set up to run automatically using a PC's task scheduler and the simple scripts at the link below. Download the scripts and put them in a folder on your desktop labelled Batch Files. Put the detectors you want to run in folder on the desktop called Detectors. Then create a txt file on the desktop with the name "go" and leave it there.

 

Start and Stop Detector

Click links to download zipped MS-DOS batch file

 

The Start Tseep-r batch file that is downloaded is set up to automatically start the Tseep-r warbler and sparrow flight call detector if that program is located at the location noted above (C:\Users\username\Desktop\Detectors\Tseep-r.exe), where the username is changed to the username of your computer. To schedule the start of a different detector (e.g. Thrush-r), right click on the Start Tseep-r icon, select Edit in the popup menu, and change the Tseep-r.exe text to the text name of the detector you would like to start and save the file with the appropriate detector name (again, this presumes the detector exe is in the Detector folder on the desktiop). The detector name will also need to be changed in and for the Stop Tseep-r.bat file.

 

To schedule nightly operation, access the PC's task scheduler by typing task scheduler in the search bar (lower left on desktop). Then open the task scheduler, select add scheduled task, and follow directions for setting up automatic tasks to run the Start and Stop detectors.