Got a unexpected lull in my morning workload and was able to find some really good info. I think these should be relatively digestible articles, they use some big fancy words, but I feel they break it down well enough for most to get the jist of things. Having some basic physics or music theory knowledge will help with really grok what they’re saying though.

This could be a decent writeup after in down the Owl of the Year if you guys want something a little more collected and simplified, but I’ll give you full links and highlights, and if there’s anything that isn’t making sense, we can of course take a look at it together, just give the word.

Brittanica - Signal Production

animals using sound communication because it is physically difficult for an animal to produce a loud sound with a wavelength much larger than itself. For this reason, small animals tend to communicate with high-frequency sounds, and only large animals use low-frequency sound signals. Aquatic animals require higher-frequency signals than do similarly sized terrestrial animals.

Think when someone shrinks or grows in a cartoon and their voice changes.

Varying the rhythm of insect stridulation or bird breathing is one way to produce different signals. Air-breathing vertebrates can also change the tension on the vibrating membranes to produce quite complicated frequency modulations. A third mechanism is to produce sounds that initially contain many different frequencies and then selectively filter out some frequencies and amplify others.

Many neat musical comparisons here! Timbre, additive and subtractive synthesis, etc!

All animal signals degrade as they propagate between sender and receiver. The farther apart the two parties, the greater this degradation will be and the less a signal will stand out from background noise. Senders can do little to reduce degradation once the signals have left the sender. However, they do have a choice of what kind of signal they produce, and evolution has often favoured choices that minimize degradation.

Sound signals transmit efficiently over large distances, around obstacles such as trees and foliage, and in dark environments. Nevertheless, sounds of all frequencies become less intense as they radiate away from a source. Higher frequencies suffer additional attenuation owing to heat losses and scattering of the sounds. Since small animals can produce only high frequencies (short wavelengths), their sound communication is often limited to short distances. Furthermore, ambient sound is often greatest at low and high frequencies, making intermediate frequencies the ones least likely to be obscured by the background.

Bandwidth issues as I referenced earlier…

Birds, even of the same species, are much more likely to use rapid temporal modulations of their calls, such as trills and buzzes, when they live in grasslands than when they live in forests. Forest birds typically produce long whistlelike notes with slow, if any, modulations.

Environment helps determine what sounds an animal will make to communicate effectively.

Detection of sound is often challenging because the received signals are faint and distorted owing to propagation. Sound traveling in air is largely reflected from solid objects, including animals, with little energy transfer. Sound traveling in water is easily transferred to aquatic animals, but because all parts of the animal vibrate in synchrony, there is no immobile reference allowing the animal to detect the vibrations. As a result, animals have had to acquire some very sophisticated adaptations to hear sounds.

More bandwidth issues.

The rest of the article goes more in depth and also covers visual and olfactory communication. Tons of great stuff in here! I’m definitely going back to read this again when I have more time.

Science Direct - Vocalization (Rest of article is paywalled)

Some birds may have anatomical or physiological limits in their ability to vocalize at higher frequency ranges to be heard over traffic noise. This could include the angle they can hold their head, how wide they can open their beak, their beak shape, and their body size. Typically, the frequencies that birds are able to produce are related to their body size. The larger the body size, the lower the frequency of the bird’s songs or call; and, the smaller the body size, the higher the frequency of their vocalizations (Ryan and Brenowitz, 1985). There is also an association between body size and amplitude (Brumm, 2004). The larger the body is, the greater the amplitude and vice versa. A bird cannot change the vocal mechanisms in their throats that allow for certain characteristics of a song to be produced

Anatomy is a key player in the amounts and types of noises animals can make.

Ugh, hitting too many paywalled articles. Let me know if this is good for an answer or if you need more. I’ll definitely be reading more about this in my own, but I did get Jennifer Ackerman’s What an Owl Knows book to read also to see what is in there. I’ve put up some interviews with her on here before and I’ve always found them interesting, so I’m trying to get that bumped up in my to do list. This is a very interesting topic though, so if you do want more clarification on anything, just let me know!