NOTE: Go to bottom of page to read about Human Hearing, Nature Sounds and Associated Vocabulary
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Our Audio Players and Graphic Representations of SoundsMany of our blog and web pages feature sound recordings. Below are descriptions of three different audio presentation styles that we use, including two that feature visualizations of the sounds (additional visualization techniques, not described here, may be used in certain situations).
EXPANDING PLAYER: Soundscape recordings that are several minutes long are usually played in a simple, expanding audio player. When closed, the player appears as a speaker icon and a right pointing arrow symbol. Click on the arrow and the player expands and begins playing the recording:
Audio clip: Adobe Flash Player (version 9 or above) is required to play this audio clip. Download the latest version here. You also need to have JavaScript enabled in your browser.
During playback, a light green progress bar will be visible, along with information about the recording. Once the recording is fully loaded (as indicated by the thin blue line at the bottom), you can click anywhere within the window and playback will jump to that specific point. If you tire of listening, hit the pause button and the player will collapse. Normally, the player must be manually clicked before a recording is heard, but on some pages the player is set to expand and play automatically when the page opens. When several of these players occur on a page, only one can be active at any one time.
WAVEFORM PLAYER: For recordings where a particular species is featured, we often use a player that displays a visualization graphic. One graphic style is an audio waveform, which is depicted as a light blue sound wave set against a black background. The greater the displacement of the light blue waveform above and below the center line, the louder the sound. The dark blue bar at the bottom tracks progress along the waveform:
Song Sparrow recorded in Berkeley County WV. 6 June 2009 © Wil Hershberger. A binaural recording0:00 / 0:00
Once a recording has loaded and is playing, you can click anywhere on the waveform and playback will jump to that spot. When several of these players occur on a page, only one can be active at any one time. Note: sound files presented as waveforms sometimes include a section that is slowed down so that you can hear intricate details that are not apparent at normal speed—the waveform of a slowed section is generally colored orange.
SONOGRAM PLAYER: When we want to display a detailed view of a recording, we include “sonogram” visualizations as part of the audio player. Sonograms (also called sound spectrograms) not only display time and loudness, but also the frequency structure of the sounds. Frequency (in hertz or cycles/second) is indicated on the vertical axis, time on the horizontal axis, and loudness by the brightness of the color (most of our sonograms use the color orange set against a blue-black background):
As with the waveform player, once the recording is fully loaded, you can click anywhere within the sonogram and playback will jump to that point. Note that we generally do not include specific time values in our sonograms, although we do tend to include a frequency scale on the right. Sonograms are often compared to notes on a musical staff, where high-pitched notes occur near the top of the staff and low-pitched notes near the bottom. When several of these players occur together on a page, only one can be active at any one time.
WARNING: If a page includes recordings in both types of players (the expanding player and the audio visualization player) you may encounter the problem of two players playing at the same time. This shouldn’t happen very often, but if does, you should disable one of the players in order to hear the other one.
Human Hearing, Nature Sounds and Associated Vocabulary
When reading blog posts and viewing sonograms you may get confused about what all the numbers and terms mean.
Frequency, hertz (Hz), noise, pure tones, octave, vibrato, timbre, are all terms that we might use to describe a sound. These terms helps us to convey more information to the reader to help you appreciated the sound more than you otherwise might.
Frequency — this is the pitch of a sounds and is defined as cycles per second (Hertz or Hz). The more cycles per second the higher the pitch of the sound. Humans can hear sounds from 20 Hz to at most 20,000 Hz (this is the extreme top end). Most people will hear from 40 — 15,000 Hz. As we get older we lose our high frequency hearing acuity due to the stiffing of the small bones in the ear. This phenomenon is called presbycusis.
Noise vs Pure Tone — If a sound is produced on one frequency it is defined as a pure tone. Conversely, sounds produced over a broad range of frequencies are defined as noise. Birds, ground, field and tree crickets, some frogs and toads, produce pure toned sounds. Katydids, wind in dry leaves and grass, the bark of some frogs, are all examples of noises.
Octave — some of our posts refer to pitch lowered sound examples. Many of these are lowered one or two octaves. An octave is the span of frequencies from one note or tone to another that is twice or half the frequency of the first. A pure tone that is 12,000 Hz could be lowered one octave to 6,000 Hz to make it more easily heard by humans. Some insects produce very high pitched songs. Saltmarsh Meadow Katydids sing at 18,000 — 20,000 Hz so if we lowered the sound 2 octaves we would be listening to the sound at 4,500 — 5,000 Hz. This is certainly a lower pitch, but it is much easier for us to hear. When sounds are pitch lowered like this we can begin to hear some of the nuances within the song that we cannot perceive at the original pitch.
Timbre — the character or quality of a sound. We know that the timbre of a barred owl is richer and lower pitched than that of a wood thrush. We can distinguish different people and different animals by the timbre of the sounds they produce. We can easily tell the different in the tremolo of a Screech Owl from that of an American Toad because to the difference in timbre of the sounds they produce.
Tremolo — a rapid variation in the loudness of a sounds. Screech owls use tremolo in some of their sounds. American toad song is a great example of a tremolo.
Vibrato — a rapid variation of a sound, a quavering from one pitch to another. Screech Owls, female Barred Owls, use vibrato in their songs and calls.
