Studying Animal Sounds
How do scientists record animal sounds? And how do scientists know what they mean? We'll explain it here, and teach you how record animal sounds, too! This lesson has three parts:
Wouldn't it be great if we could invite birds into a recording studio so we could make perfect recordings of their sounds? A relatively cheap microphone can make clear, accurate recordings if it's placed close to the sound source, and in a sound studio there are no wind, traffic, or other background noises. Unfortunately, wild birds simply refuse to cooperate. To capture bird sounds in the wild, ornithologists can use two kinds of tools: a directional microphone or a parabolic microphone.
Directional microphones are long--the longer the better. They pick up any sounds that hit them, but the ones they pick up best are the ones directly in front of them. These are especially useful for songs with low frequencies, like owl hoots, and for capturing a variety of general sounds in an area. They are easy to carry and use.
Most scientists record into cassette tape players, which are reasonably small for lugging around and work well just about anywhere, from deserts to rain forests. Digital tape recorders ("DAT machines") make better recordings, but are much more expensive and for some reason the tape can get stuck easily when it's humid, so they have problems in rain forests.
This: Taping an Animal!
After you make some recordings, take turns quizzing your classmates to see who can name the animals that made the sounds. Start a classroom sound library to save your recordings.
Figuring Out What Animal Sounds Mean
Any time most birdwatchers are outdoors, they are paying attention to natural sounds. After a while, they can recognize most of the insects, frogs, mammals, and birds in their area simply by their voices. Birdwatchers quickly notice that there are many more sounds in spring and early summer than any other time of year, and soon start noticing that each bird gives some sounds in specific situations.
When a scientist studies a species, s/he describes each vocalization heard along with the date, time, place, and exactly what the animal was doing when the sound was produced. Little by little, these notes can help the scientist to discover patterns. Recording these sounds and looking carefully at spectragraphs of them makes it a lot easier for other scientists to compare notes. For example, one scientist might write in his notes that a chickadee call sounds like "zeet" to him; another scientist somewhere else might write in her notes that a chickadee call sounds like "tsleet" to her; and a third scientist might write that the exact same sound is a "sheet." Comparing the spectragraphs they can quickly discover that the sounds are all the same call!
Little by little, patterns of meaning become clear. When scientists think they've discovered the meaning of a vocalization, they write a short article about it, including spectragraphs, and send it to a scientific journal. Other knowledgeable scientists will jury the article, making sure it's accurate as far as they know, and if in their judgment the article has solid new information, it will be published. Then when people interested in that species read the journal article, they may have interesting thoughts or discoveries that add to the information, and they will write additional papers. Little by little, people have figured out what a lot of animal sounds mean. But there are many more sounds to study. Maybe you will be the one who figures out what some fascinating animal sounds really mean!
This: Be an Animal Sound Sleuth!
To Learn More
You can learn more about natural sounds at:
To learn about vocalizations of some species, see Journey North's