What Makes Birdsong Sound Pleasant? Tübingen Study Finds Clues

Dr. Nadine Kalb and Dr. Christoph Randler of the University of Tübingen in Germany have identified acoustic traits that make some birdsongs sound more pleasant than others, in a study published in Frontiers in Bird Science. Understanding this could help improve park design and stressful spaces like waiting rooms, and support conservation built around pleasant-singing birds, they said.

The scientists recruited 84 people and played them short clips of 123 songs from wild birds common in Germany, who rated each clip's pleasantness on a scale of one to five and answered questions about their birding skill and interest in birds. Researchers measured each song's amplitude (loudness), frequency (pitch), complexity — the number and variety of elements — and bandwidth, the range between its highest and lowest frequencies.

Songs with a narrower bandwidth, greater complexity, a higher frequency and a relatively low amplitude were rated more pleasant, and the highest-scoring songs avoided a frequency range where human hearing is especially sensitive. A blackbird's song was rated most pleasant; a barn owl's, least pleasant. People who valued birds more rated songs more highly, but their level of birding knowledge made no difference. "You don't have to be a 'bird person' to find bird sounds beautiful," said Kalb, the study's lead author, adding that recognizing birds by sight or song did not affect ratings, a sign that birdsong enjoyment is tied to something more fundamental than knowing what one is hearing.

The team compared results with an earlier study of 21 overlapping species on how restorative — aiding recovery from mental fatigue or stress — different birdsongs were. Blackbirds' songs, the most pleasant in the new study, were also rated highly restorative in that earlier work, the researchers said.

The researchers said they could not test whether call rate — how often a bird calls — affects pleasantness, and plan larger studies with broader samples, including more men, different cultures and experienced birdwatchers.