Why the Blackbird’s Song Sounds So Pleasant to Human Ears, Scientists Explain

A quiet, ordinary moment happens every spring: a blackbird starts singing outside a window, and something in the listener’s chest loosens just a little. Meanwhile, a barn owl’s screech from the same backyard might send a chill up the spine instead. Bird lovers have long sensed that some birdsong feels soothing while other bird sounds feel jarring, but nobody had pinned down exactly what makes one call pleasant and another unpleasant until researchers in Germany decided to measure it.

A team based at the University of Tübingen played recordings of 123 European bird species for German adults and asked a simple question: how pleasant does this sound? Then they went back and dissected each recording note by note, measuring pitch, loudness, and the range of sound packed into each call. Writing in the journal Frontiers in Bird Science, the researchers described what emerged as close to a recipe for what makes a bird sound “nice” to the human ear, and the common blackbird came closest to that recipe, while the barn owl landed at the opposite end of the scale.

Findings like these reach past birdwatching circles. Cities and parks are increasingly designed with human well-being in mind, and natural sound is a big part of that. Knowing which acoustic traits actually calm people down, rather than just guessing based on which birds look pretty, could shape how green spaces are planted, managed, and even marketed.

How Scientists Measured Which Bird Sounds Are Pleasant

Researchers recruited 84 adults through a university mailing list, ranging in age from 19 to 81, with an average age of about 34. Most participants were women. Small groups sat in a quiet room, received tablets and headphones, and listened to 15-second audio clips of 123 different European bird species, played in random order with no hints about which bird was making the sound. After each clip, listeners rated how pleasant it sounded on a scale of one to five.

Participants also answered questions about their own relationship with birds. Some questions gauged birding skill, such as how many species they could identify by sight or sound. Others measured something different: how much a person simply likes birds, for reasons like finding them pretty to look at or enjoying their song. These two things, skill versus fondness, turned out to matter in very different ways, which is one of the study’s more surprising results.

On the technical side, scientists used audio software to break each recording down into its basic sound properties. They measured the pitch range in each call, the loudness, and how many distinct sound elements appeared within each 15-second clip, a rough stand-in for how varied each call sounded.

What Makes a Bird Call Sound Pleasant to Humans

Averaged across all 84 listeners, the overall pleasantness score for bird sounds landed at about 3.13 out of 5. But individual species varied enormously. Blackbird songs pulled in the highest average rating at 4.52 out of 5. Barn owl calls scored the lowest, at just 1.32 out of 5, a sound most listeners found closer to unpleasant than pleasant.

When researchers dug into why, a clear pattern emerged. Bird calls with higher minimum and peak pitches were rated more pleasant, while calls that were louder, or that swept across a wider pitch range, were rated less pleasant. In plain terms, quieter, higher, narrower-range sounds won out over loud, low, sprawling ones. This fits with older research on human hearing: the ear is especially sensitive to a mid-range band of pitches and registers sounds there as louder and harsher than they really are, and the bird calls people liked best tended to fall outside that band.

Variety in each call mattered too, but in a straightforward way: birds whose calls contained more different types of sound elements packed into that 15-second clip tended to be rated as more pleasant than birds that repeated the same simple note over and over. Simply having more total sounds crammed into the clip did not help, though. People responded to variety, not sheer quantity.

Perhaps the most interesting twist involved the listeners themselves rather than the birds. Age, gender, and birding skill level had no measurable effect on how pleasant someone found a given bird sound. Someone who could identify hundreds of species by ear was no more or less likely to enjoy a robin’s song than someone who couldn’t tell a sparrow from a finch. As the researchers put it, pleasantness ratings were “not dependent on knowledge or bird-related activities.”

What did matter was simpler and more emotional: how much a person said they liked and valued birds in general. Listeners who agreed with statements like liking birds because they are pleasant to look at or listen to consistently rated the sounds as more pleasant overall. Liking birds, it seems, colors how pleasant their voices sound, regardless of how much someone actually knows about them.

Researchers also tied their findings to earlier work that measured how “restorative” people find bird sounds, meaning how much a sound helps someone mentally recharge. Comparing scores for 21 species that appeared in both studies, the team found a solid positive relationship between how pleasant a bird sounded and how restorative it had previously been rated.

Why Pleasant Bird Sounds Matter Beyond the Lab

None of this means barn owls are bad or blackbirds are objectively superior birds. Owls hoot and screech for reasons that have nothing to do with human ears, and their calls serve them perfectly well in the wild. The research points to something simple: when people design parks, plan urban green spaces, or decide which animals to champion for conservation, the sound of nature deserves as much attention as its sight. A songbird with a varied, higher-pitched, moderate-volume call may simply make a shared green space sound more welcoming, and that alone could be worth building around.