Sound Perception

We are constantly surrounded by sound and sound perception can be vastly different from person to person. Sound is all around us and we have ways to measure it. Some people might be familiar with the term Sones. In a previous post we went into depth on sones (What in the world is a Sone – how loud is my exhaust fan?). More people are probably familiar with the term decibel but might not know what it really is. The book definition of a decibel is a unit used to measure the intensity of a sound or the power level of an electrical signal by comparing it with a given level on a logarithmic scale. With these sound measurements we can get an idea of how loud or quiet a product will be. For instance, it would be logical to think that a fan that is 3 sones will be significantly louder that one that is 1 sone. Generally that would be true, but there are more factors involved. We are going to take a look at a couple main ones.

What environment is the fan installed?

Most exhaust fans are going to be placed in bathrooms. Generally bathrooms are going to have a large amount of area tiled or have hard surfaces. There is very little noise absorption in a bathroom. This is going to cause the fan to sound louder than if it was installed into say a living room that has wall-to-wall carpet with fabric couches and chairs. A great way to demonstrate this is to play music through your cell phone holding it at arms length. Now take an empty plastic bucket and put your phone inside it. Did you notice any difference in sound? The volume did not change, but the perception of sound did. Now do the same thing but this time put a towel inside the bucket first – any difference?

Ambient Sounds

We perceive noise differently depending on the amount of ambient sound around us. When an exhaust fan is installed into a bathroom that is isolated from the rest of the home, any sounds inside the room are going to be heard more easily. Here is another comparison for you. When you are walking on a busy city street, the sounds of cars running, even honking sort-of blends in. Now think about walking on a back road and the sound of the same car is going to be perceived as louder – especially if it honks it’s horn.

So what do we do with all this information about sound perception?

Having this knowledge will hopefully help when it comes to purchasing your next exhaust fan. Take into consideration how your bathroom is laid out, what materials are being used, is there anything in the room to absorb sound, etc. If your bathroom is going to be floor to ceiling tile, with a glass enclosed shower, the perceived sound is going to be more than if that same fan is installed into a bathroom with tile only in the shower area, large bath mats and a cloth curtain. To get the same perceived sound level, you will need to chose a fan that is considerably quieter.