In the grand orchestra of nature, waterfalls stand as majestic percussionists, their sound a harmonious blend of power and serenity. But what orchestrates this captivating sound? The answer lies in the basic principles of acoustics. When water cascades over cliffs and crashes into pools below, it creates vibrations in the air. These vibrations, like the strings of a violin being bowed, generate sound waves. The intensity and pitch of these sounds vary with the waterfall’s height and the volume of water, much like how the dynamics and timbre of music change with the force and speed of a musician’s play.
Waterfalls and the Spectrum of Sound
The white noise of waterfalls
Waterfalls, in their endless descent, produce what is often termed ‘white noise.’ This term, borrowed from audio engineering, refers to a sound that contains every frequency within the range of human hearing, all at equal intensity. In a waterfall, this phenomenon arises from the countless water droplets striking various surfaces simultaneously, each contributing a unique frequency to the overall sound. This creates a soothing blanket of noise, masking unwanted frequencies, much like how white light blends all colors.
Listen to Hengifoss in East Iceland:
What about pink noise?
Contrasting with white noise is pink noise. Characterised by a frequency spectrum that decreases in intensity with increasing frequency, pink noise is richer and softer, often associated with natural sounds like rustling leaves or steady rain. However, waterfalls rarely produce pink noise due to their more chaotic, less uniform structure. The random and tumultuous nature of falling water doesn’t allow for the even distribution of energy across frequencies that pink noise requires.
One of the more difficult sounds to catch – the Háifoss waterfall in southwestern Iceland. To reach it, it takes two hours by car from Reykjavik, including a dozen or so minutes on a very bumpy road, and then eight kilometers by foot through the mountains. Although, one would like to say, these are not the mountains, but the scenery from a fairy tale. According to legends, the Fossárdalur valley, where the waterfall is located, is inhabited by ogres that fish there. They must not be disturbed, as one boy who camped in the valley found out. For fun, he threw a stone into the river and the ogres, offended by it, wanted to devour it. Fortunately, his friend saved him from that. Besides, the valley is famous for having several scenes for Game of Thrones filmed in the area. The waterfall is 121 meters high and is probably Iceland’s third tallest waterfall. Its name in Icelandic means “high waterfall”.
Nature’s acoustic
The sound of a waterfall is not a fixed entity but a fluid composition shaped by its environment. The surrounding topography – from the shape of the cliff to the depth of the pool – acts as a natural amphitheater, amplifying and molding the sound. Rocks and crevices disrupt and scatter sound waves, adding complexity to the waterfall’s acoustic signature.
When I talked to the people of Iceland (and they were not only Icelanders) about the sounds from the island, I remembered the question of whether the sounds of the waterfalls could be distinguished. – Of course they can – said the friend – I live near Gullfoss, so I know exactly what it sounds like. Gullfoss rumbles. And Skogafoss, for example, hisses like a shower.
Just as a symphony varies in its movements, waterfalls too have diverse sound profiles. Factors such as the volume of water, its speed, the height of the fall, and even the wind play crucial roles in determining whether a waterfall roars deeply, rumbles menacingly, or whispers gently like a rain shower. These variations can be likened to the different instruments in an orchestra, each bringing a unique sound and character to the whole.
I admit that I did not appreciate this waterfall. I even apologized to it for that (yes, I stood in front of it and said aloud: sorry to you, waterfall). For the first time, although I have lived in Iceland for almost 5 years, I dared to walk around it, that is to enter a large cave in its “back room”. Usually people came out of there wet, and somehow I was never ready for it. It turned out that behind the Seljalandsfoss stream it is maybe wet, but also very nice – intimate, as if you could hide there from the world. Seljalandsfoss flows from the Eyjafjallajökull glacier, the same glacier where the world-famous volcano is dormant. It also has a very characteristic, “scratching” sound, which is made by the water hitting the rocks just below your feet.
