Soundscape

Today in our general studies class, we all went up to the rooftop and did ear cleaning.

Ah, that sounds like a wonderful experience. It must have involved closing your eyes quietly and writing down the sounds you heard. Did your teacher explain why you do that?

Yes, they said it was "to raise awareness of creating a comfortable sound environment by taking an interest in the sounds around us."

You don't need to go to a concert or some special place to test your sensitivity to sound; there are plenty of opportunities in your everyday life.
Did you make any new discoveries?

I don't usually go up to the roof, but you can hear sounds from quite far away. Especially when there are no cars on the surrounding roads, you can hear birds chirping on the hill behind the house, and there are all sorts of sounds caused by the wind, like the railings rattling or leaves rubbing together—all sounds I normally wouldn't notice.

It's amazing how you can hear all sorts of sounds when you concentrate on them. The rooftop offers a wide view that extends far into the distance, so you can hear sounds that are obscured by the building and not heard in the schoolyard or other parts of the school. Were there any unpleasant sounds among them?

Hmm, I didn't find it particularly unpleasant, but it was noisy when trucks passed by occasionally. However, I discovered that there are many different kinds of car sounds. When cars pass by on the road in front of the school when the traffic light is green, it's a high-pitched hissing sound, and when cars that have been stopped at the light start moving again, you can hear a fairly low sound, and I realized that it differs depending on the type of car.

I see. You've noticed something interesting. When a car is driving at a constant speed without pressing the accelerator, the noise outside the car is mainly the sound of the tires contacting the road, with a large component in the 600 Hz to 1000 Hz range. As you said, when accelerating from a standstill, the engine noise is louder. The pitch (frequency) of that sound depends on the engine's rotational speed (number of revolutions per minute).

Yeah, I noticed that the sound of acceleration changes in tone as the speed increases.

Besides this ear cleaning, another common part of sound education is something called a sound walk. Did you not do that?

Yeah, today was just ear cleaning. What's a soundwalk?

This project involves walking through a specific area of a region, focusing on the sounds present, in order to discover sounds unique to that place. Sound isn't just about physical quantities like volume or pitch; it's also about subjective perceptions, like whether a sound is pleasant or unpleasant. While some sound sources, like cars, move around, walking through a region allows us to discover distinctive sounds that can only be heard in that specific location. We'll record these sounds—sounds that symbolize the region, sounds people feel attached to, and even sounds they find unpleasant—without discrimination.

It would be interesting to walk around with a sound level meter and measure the noise levels.

That's true. But with soundwalks, it's important to rely on people's ears and sharpen their senses.

I see, it's just like ear cleaning. I tend to think that I can't understand anything unless it's quantified.

Up until now, noise from cars and airplanes, as well as natural sounds in the environment, have been evaluated using physical quantities such as dB. As Oto says, if we don't quantify it, everyone can't evaluate it the same way. However, sound has both a physical aspect as air vibration and a sensory aspect such as pleasant or unpleasant sounds. In other words, it can be said that sound presents meaning that each person perceives in that sound. For example, we may feel autumn from the sound of insects, or feel a sense of coolness from the babbling of water. Of course, it is important to measure and understand the physical quantity, but before that, there is a growing interest in considering what meaning that sound gives to people.
A Canadian composer and researcher named R. Murray Schafer proposed the concept of soundscape, which, as I just mentioned, re-examines the semantic value of sound and demonstrates an approach that considers the sound environment as a culture.

Soundscape?

Yes, it's a neologism meaning "soundscape," created by applying the sounds of words like "landscape" or "cityscape," which are used to mean scenery or urban landscape.

I see, so it's the scenery... If you record the sounds you find on a soundwalk on a map of the area, you can create a soundscape map.

That's right. In soundscape, we call it a sound event map, and by creating this sound map, we can find out what kind of sounds are where in a particular area. I think it's an important effort to raise awareness of the sound environment among local residents. Sound event maps show semantic information, but actually, physical sound maps are also being actively created, especially in Europe. In the EU, in response to the growing awareness of the health risks posed by environmental noise, the Environmental Noise Directive was issued in 2002 as a basic common guideline for addressing noise, and one of its features is the creation of noise maps for areas with a population of 250,000 or more.

Is a noise map something that shows the numerical values of sound measurements?

Basically, it's all calculation. Various conditions are input, such as terrain and building information, sound source size, road noise, and traffic volume information, and the attenuation of sound due to propagation from the sound source to the receiving point is calculated, and then the daytime and nighttime conditions in residential areas where people live are measured.
It represents the average noise level over time on a map. It's common to use different colors to indicate the magnitude of the level.

I see, so the amount of noise can be represented on a map like this. It would be interesting if we could also represent the meaning of the sound.

That's true. In cities, the noise around roads is so loud that even if there are unique sounds specific to a region, they're often drowned out by traffic noise. In that sense, if those unique sounds were to be rediscovered, a map that represents both the physical and semantic aspects would become meaningful.