After last week’s calibration in the anechoic chamber, this week we tested the SM4 acoustic recorders in the field. We took four of the recorders and played a series of cardinal sounds at varying distances.
Before we started the testing, the first thing we did was use an iPhone app to determine the decibel level of three different locations that were varying distances from Highway 360, at the western boundary of Wild Basin. This helped us determine the baseline level of anthropogenic (man-made) noise before getting started. Once an average decibel level was recorded, we played the cardinal sounds at 10m, 30m, and 50m away from the SongMeter SM4 recorders.
We then took the SD cards and the units back to the computer lab in the Wild Basin Creative Research Center and looked at the recordings on the Wildlife Acoustic analysis software, Kaleidoscope. This software helps you quickly convert files, sort and categorize data by species, and review a visualization of the sound recordings. It was interesting to look at the spectrograms on the computer and see the variations in sound intensity over distance. The spectrogram shows you the intensity of sounds at various frequencies over time. It was also really interesting to compare the spectrograms for the “pink noise” that we recorded in the anechoic chamber to the spectrograms of a bird song. Pink noise covers all the sound frequencies at once, so it shows up as a big block on the spectrogram. On the other hand, a bird song has a distinctive pattern that moves across a range of frequencies in a short span of time.
There was some user error with the recorder settings that we will sort out and hope to eliminate next time in the field. It was fun to finally get to test the equipment in the field and visualize what the recordings look like on the computer. There is going to be a learning curve with using these new techniques, equipment, and software, but it’s really helpful to test things out in the field prior to formal data collection. Next step we are deploying the units in early March to start gathering data.
(Here is a spectrogram of a Northern cardinal song played at varying distances away from the SM4 sound recorder. You can see the repeating up-and-down pattern of a cardinal song at several points in the recording. The pattern is a bit more faint on the right side because the song was played farther away (and was therefore less intense) from the recorder)