Why Some Bird Songs Sound Better Than Others: The Acoustic Recipe for Pleasant Birdsong

There is a reason the fluting melody of a common blackbird at dawn feels restorative while the rasping shriek of a barn owl can set teeth on edge. A new study from the University of Tübingen, published in Frontiers in Bird Science, has systematically dissected the acoustic anatomy of bird vocalizations to determine exactly which physical properties make some bird sounds feel pleasant to human listeners and others decidedly less so. Drawing on recordings of 123 European bird species and the ratings of 84 German adults, the research offers one of the most comprehensive accounts to date of how frequency, amplitude, bandwidth and complexity combine to shape our emotional response to the sounds of the natural world.

The research team, led by Nadine Kalb and Christoph Randler, invited participants into a controlled laboratory setting where they listened to 15-second recordings of wild bird vocalizations, all taken from the widely used reference collection Die Stimmen der Vögel Europas by Bergmann and colleagues. Each participant rated the pleasantness of every sound on a five-point scale, from not very pleasant to very pleasant, without being told which species was singing. Recordings were played in randomized order through headphones at a fixed volume, and listeners could replay each clip as often as they wished before committing to a judgment. The species pool spanned the breadth of the German avifauna, from garden songbirds to owls and waterbirds, ensuring that the results reflect the acoustic diversity people actually encounter in Central European landscapes.

The ratings revealed a striking spread. The average pleasantness score across all species was 3.13 on the five-point scale, but the extremes were dramatic. The common blackbird, with its rich, fluty warbling, earned the highest mean rating of 4.52, while the barn owl, whose eerie hissing screech bears little resemblance to melodic song, received the lowest at 1.32. These extremes are more than trivia: they anchor a quantitative question about what, physically, separates a beloved dawn chorus voice from a sound many people would rather not hear at dusk.

To answer it, the researchers turned to detailed acoustic measurement. Using the bioacoustics software Raven Pro, they inspected every recording in spectrogram view and manually marked each sound element, defined as a visible trace without a temporal gap. For every element they extracted four frequency-domain parameters: the low frequency, below which the lowest 5 percent of the element’s energy falls; the high frequency, below which 95 percent of the energy is contained; the peak frequency, where spectral power is maximal; and the 90 percent bandwidth, the frequency span holding the bulk of the element’s energy. From the waveform they also derived minimum, maximum and peak amplitudes, capturing how loud each element was. Finally, they counted the total number of elements in each 15-second clip and the number of distinct element types, using the latter as an objective proxy for what psychoacoustics researchers usually measure subjectively: sound complexity.

Because seven correlated acoustic variables are unwieldy to interpret, the team ran a principal component analysis with varimax rotation, validated by a parallel analysis, which distilled the measurements into three interpretable components. The first, an amplitude component, bundled minimum, maximum and peak amplitude together. The second, a frequency component, captured low and peak frequency. The third, a bandwidth and high-frequency component, combined bandwidth with high frequency. Feeding these component scores into a multiple regression against the mean pleasantness rating of each species produced a model that explained a substantial 46.8 percent of the variance in pleasantness, with all three components emerging as significant predictors.

The direction of the effects tells a coherent psychoacoustic story. Sounds with higher low and peak frequencies were rated as more pleasant, consistent with longstanding findings that low-frequency sounds are harder to ignore, more difficult to habituate to, and often perceived as annoying or even aggressive. Conversely, sounds with lower high frequencies and narrower bandwidths scored better, which aligns with earlier work showing that the human auditory system is maximally sensitive between roughly 2.4 and 5.5 kilohertz; sounds in that range are perceived as louder and more intense, and therefore less pleasant. The most highly rated vocalizations in this study had low and high frequencies that largely avoided that uncomfortable zone. Lower amplitudes also predicted higher pleasantness, echoing previous reports that louder bird sounds are considered less restorative, although the authors urge caution here because the commercial recordings did not follow a standardized recording protocol, so amplitude differences may partly reflect recording conditions rather than the birds themselves.

Complexity added its own independent contribution. In a separate regression, the number of different element types within a vocalization significantly predicted pleasantness, whereas the sheer total number of elements did not. In other words, it is not how often a bird vocalizes but how varied its repertoire of sounds is that listeners find appealing. A follow-up model including all three acoustic components alongside complexity and element count confirmed that the complexity effect persisted independently of the spectral and amplitude characteristics, suggesting that variability in vocal output is a genuine dimension of acoustic appeal rather than a byproduct of frequency or loudness. This dovetails with earlier findings that people prefer sounds of moderate complexity and rate more complex birdsong as more restorative.

The study also probed the listeners themselves. Age, gender and, perhaps surprisingly, birding specialization had no significant effect on pleasantness ratings, indicating that appreciating a beautiful birdsong does not require expert knowledge or years spent in the field. What did matter was how much participants valued birds in general. Those who agreed more strongly with statements such as liking birds because they are beautiful to look at, pleasant to listen to, or helpful for feeling good rated the vocalizations as more pleasant overall, with a positive correlation between the two measures. The authors suggest that people who spend more time in nature-related activities accumulate positive associations and memories with bird sounds, which color their perception. Notably, the pleasantness ratings from this German sample correlated positively with the Perceived Restorative Potential scores reported for 21 overlapping species in earlier research by Ratcliffe and colleagues, hinting that pleasantness and restorativeness are related, though not identical, constructs.

The implications reach beyond the laboratory. If not all bird vocalizations contribute equally to human well-being, then soundscape quality in urban parks and green spaces may depend not just on how many birds are present but on which species. Management practices that support acoustically pleasant species, those with higher low frequencies, moderate loudness, narrow bandwidths and varied repertoires, could enhance the restorative value of recreational areas. The authors also raise the provocative idea that acoustic pleasantness represents an additional dimension of wildlife charisma. Conservation programs have long relied on visually appealing flagship species to rally public support; incorporating how a species sounds into that calculus might strengthen conservation communication and deepen human connection to nature.

The authors are careful to note the limits of their findings. The participant pool was modest and skewed toward women, the ratings come from a single cultural context, and individual differences in perception were not explicitly modeled, leaving room for future work with larger, more balanced samples and mixed-effects approaches. Still, the core message stands: the pleasure we take in birdsong is not mysterious. It can be traced, element by element, to measurable properties of sound, and understanding those properties gives planners, conservationists and anyone who loves a dawn chorus a new tool for protecting the acoustic richness that makes natural spaces restorative in the first place.

Subject of Research: Acoustic parameters of bird vocalizations and their perceived pleasantness by human listeners

Article Title: Analyzing the acoustic parameters of bird vocalizations and their perceived pleasantness by humans

Article References: Kalb, N., von Lücken, G., Lukanowski, J., Dechant, F., & Randler, C. (2026). Analyzing the acoustic parameters of bird vocalizations and their perceived pleasantness by humans. Frontiers in Bird Science, 5, Article 1794594. https://doi.org/10.3389/fbirs.2026.1794594

Image Credits: AI Generated

DOI: 10.3389/fbirs.2026.1794594

Keywords: birdsong, acoustics, psychoacoustics, sound pleasantness, restoration, birding, soundscape, conservation, frequency, amplitude, complexity, human perception