Low buzzes, screaming babies, pounding beats and soft whispers: sound consists of many different variables. Some even might be the same amount of decibels, but feel louder. How does all that work?

Remember the old days, when we needed to know when a mammoth was coming so we could save our Flintstone-age asses? Ok, maybe that was a while ago, but our bodies haven’t changed too much since those times. Thus, our ears are very very sensitive. And we can identify many different types of sound and noise. As you you might remember from physics class in highschool, sound comes in waves, caused by a vibrating object like vocal chords or a guitar string. The vibrations move the air, that reaches our ears and is transferred into information. Voilá. We hear. But what do we hear?

Pitch it, baby

The sensation of a frequency is what we call ‘pitch’. A high pitch sound refers to a high frequency wave, the low pitches are formed by slower waves. We measure frequency in Hertz (Hz). The human ear is capable of detecting sound waves with a wide range of frequencies, ranging between approximately 20 Hz to 20 000 Hz.

The high wave

But pitch is not the only quality of sound: it’s also a transmission of energy. The more energy is used, for instance, to stroke a guitar string, the higher the waves. The highness of a wave is called the amplitude, and that is responsible for sound intensity, the volume and distance the sound waves travel. Sound intensity, so the pressure of the moving air, we measure in decibels (dB). As you can read in this cool article, decibels do not work on a linear scale.

Here’s a little list of common sounds and their dB’s:

• 0 The softest sound a person can hear with normal hearing
• 10 normal breathing
• 20 whispering at 1 m
• 30 soft whisper, nature sounds at a distance
• 40 quiet office, library
• 50 rainfall, normal office
• 60 normal conversation, electric toothbrush
• 70 freeway traffic, TV audio, vacuum cleaner
• 80 toilet flush, ringing phone, food blender
• 85 heavy traffic, noisy restaurant or office
• 90 shouted conversation, motorcycle at close distance
• 110 disco, rock concert, shouting in ear, baby crying, car horn
• 120 chainsaw, ambulance close by, thunder
• 130 percussion, power drill
• 140 airplane takeoff
• 150 fire cracker, balloon pop
• 170 shotgun, rocket launch

As you see, a coffee machine and a ringing doorbell might have the same dB’s measured. But hey: they feel different. So, volume and intensity are two qualities of sound – although it is safe to state that the more intense sounds will be perceived to be the loudest sounds. Also the frequency affects our perception: a pumping bass from a stage and a chainsaw may be on the same level, we experience higher, piercing sounds as more annoying than lower buzzes.

Beep, beep

But that doesn’t mean lower sounds are safer for our precious little ears. Whether a sound is damaging to the ears depends on the amount of dB’s and the time of exposure. Already the low volume of 85 dB’s can be harmful to your ears. And of course also the frequency plays a role: exposure to the same frequency for a long time damages your ability to hear that frequency. So don’t forget to use hearing protection whenever you can. Better safe, than beeping.