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Science Series Part 4: Intensity

Dr. Emily Martinson, Au.D., Ph.D.

Grab your pocket protectors and plastic glasses, it’s nerd time!  After a couple of weeks talking about hearing aids, this week we jump right back into the physics of sound.  Remember, the more you know about sound, the more you can understand about the way you hear, which can help you hear your best.  This week’s topic is intensity, a critical component of the all-important sound wave.

As discussed in Science Series Parts 1, 2, and 3, sound is a physical vibration through a substance (most commonly air) that produces a wave containing the properties of frequency, intensity, and wavelength.  As a reminder, frequency is the rate at which the vibration occurs.  Today’s topic, intensity, is the force of the wave.

When many of us think of intensity, we think of how difficult something is.  For example, if you are a fitness buff and have a really intense workout, first of all, keep up the good work!  Second of all, many of us would describe your intense workout as very difficult and challenging, and requiring a lot of power.  The physical property of intensity is very similar.  From a scientific perspective, intensity can be defined as the strength or power of the sound, and is measured in decibels.

When we look at the sound wave, the intensity is the height of the wave, or up and down motion.  As listeners, we interpret intensity as the loudness of the sound.  Take for example a bell ringing.  The bell always has the same pitch (or frequency), but can have a different loudness depending on how hard you ring it.  If you ring it very softly, your brain interprets that as a low volume, or low intensity.  If you are waving your arm as fast as you can and ring it very loudly, your brain interprets that as a high volume, or high intensity.  (Maybe don’t do that one in public… people can be so judgmental…)

Intensity is very important to audiologists and hearing care professionals because when we test someone’s hearing, we are looking for the lowest intensity sound that they can hear.  In other words, we want to know how soft a sound can be before you cannot hear it any more.  This gives us important information about the functioning of your ear.  Make sure to check with your audiologist or hearing care professional for more information!