These pages are an interactive version of the introduction to the Peterson Field Guide to Bird Sounds. Here you will learn how to visualize sounds and how to describe them in words.
- Visualizing sound
- The five basic pitch patterns
- The four basic patterns of repetition and speed
- Changes in speed and pitch of whole songs
- Complex series
Visualizing Sound (p. 6)
Visualizing bird sounds makes it easier to identify them, because the aspects of bird sound that are important for visualization are the same ones that are important for identification: pitch pattern, speed, repetition, pauses, and tone quality. Creating a mental image of the sound makes it possible to look up the sound in the visual index of the book (p. 495), where similar sounds are grouped by their visual pattern.
How to see it
The best way of depicting bird sounds visually is the spectrogram (often called the Sonagram), a computer-generated graph of sound frequencies across time. Below, compare how the same familiar tune appears in two different visual depictions: standard musical notation on the left, and a spectrogram on the right:
Musical notation places notes on a staff, while spectrograms measure the frequency of sounds in kilohertz (kHz), but the basic principle is the same: they both read from left to right, with high notes near the top of the chart and low notes near the bottom. On a spectrogram, the more horizontal space a note takes up, the longer it lasts in time.
Most spectrograms in the Peterson Field Guide to Bird Sounds conform to the scale above, with the top of the spectrogram at 10 kHz (near the upper limit of hearing in most adults) and numbers across the bottom marking intervals of one second.
Real spectrograms vs. spectrogram symbols
The Peterson Field Guide to Bird Sounds uses two types of visualizations: real spectrograms in the species accounts,
where accuracy and detail are important; and spectrogram symbols in the visual index, where basic patterns and similarities are more important than detail.
The five basic pitch patterns
Unlike music, bird sound identification does not require attention to the precise pitch of notes; more important is how the pitch changes. All bird sounds can be described with just five basic pitch patterns (or combinations thereof), which can be visualized this way:
- Monotone sounds do not change in pitch, and appear horizontal on the spectrogram.
- Upslurred sounds rise in pitch, and appear tilted upward.
- Downslurred sounds fall in pitch, and appear tilted downward.
- Overslurred sounds rise and then fall in pitch, appearing and sounding highest in the middle.
- Underslurred sounds fall and then rise, appearing and sounding lowest in the middle.
The four basic patterns of repetition and speed
The key to hearing and visualizing the repetition and speed of bird sounds lies in two questions:
- Does the bird ever sing the same note twice?
- Are the notes slow enough to count, or too fast to count?
Together, these two questions make it possible to identify four basic patterns of bird sound: phrases, series, warbles, and trills. Phrases and series are slower sounds, with individual notes slow enough to count; phrases contain unique notes that are not repeated, while series consist of one note repeated over and over. Warbles and trills are faster versions of phrases and series, with notes too fast to count (faster than about eight notes per second). At this speed, unique notes run together into a single warbled sound, and similar notes merge into a trill.
Even tremendously long and complex bird songs can be described as a combination of phrases, series, warbles, and trills. These four patterns form the most important building blocks of the visual index in the Peterson Field Guide to Bird Sounds.
The following examples illustrate these four basic patterns with real spectrograms:
Examples of phrases (unique notes, slow enough to count)
Examples of series (repeated notes, slow enough to count)
Examples of warbles (unique notes, too fast to count)
Examples of trills (repeated notes, too fast to count)