You’ve probably heard online that “white noise” is fantastic for sleep, maybe you did your own research and found out that “pink noise” is better, what if I told you that there is an even better “noise” that you probably haven’t heard of.

First, we need to know how noise works
I think we all have experienced the unpleasantness of listening to a broken tap. The “drip drip drip” grabs our attention. Then we anticipate the next “drip” which keeps us alert. In fact, dripping taps have been used as a form of war torture.

But what if we had 1000 dripping taps? This would sound like rain on a tin roof. Ahhh, what a pleasant relaxing sound. Many individuals listen to rain sounds to help them concentrate, relax and sleep. How is it possible that more of something unpleasant can be so appealing?

Disengaging from noise

We hear rain as a constant unchanging sound instead of 1000 individual raindrops. As the rain continues, we learn that the information is no longer important and habituate to the sound. From an evolutionary perspective, changes in our environment should demand more attention than unchanging background sounds. This is a reason why unexpected, irregular or intermittent sounds are so distracting.

Auditory masking of unpleasant sounds with broadband timbres

Broadband timbres are sounds that cover a large proportion of frequencies in our hearing spectrum. Imagine playing every single note on a piano at once excluding one single pitch, it would be very difficult to know which note is missing. Like a mask hiding one’s face, broadband timbres can mask background sounds. The sound of rain can mask the sound of a dripping tap.

This benefits sleep because sounds that might wake us up or distract us from falling asleep are hidden behind a wall of sound. One study compared silence, recordings of hospital wards and recordings of hospital wards masked by broadband timbres on sleep quality of participants. The authors of the study found that participants who listened to recordings of hospital wards had decrease sleep quality than when sleeping in silence. When the hospital recordings included broadband timbres, the impact on sleep quality and number of arousals was significantly decreased.

Why is “…” (colour) noise effective at masking unpleasant sounds

White noise is often used for masking because it covers the entire hearing spectrum at equal volume. This sound should be flat (i.e. heard evenly across all frequencies), however this is not the case because our ears are more sensitive to different frequencies. In general, we hear higher pitch sounds as louder. This is why white noise sound “hissy” and unpleasant. Pink noise accounts for this as the higher pitch frequencies are quieter, which we hear as more even sounding.

The ultimate noise for masking

To go further we must look at the Fletcher-Munson curves. These curves attempt to depict how loud a frequency must be for us to perceive it as equal volume to other pitches. The ultimate noise for masking is GREY NOISE because it is designed to have an inverse relationship with the Fletcher-Munson curve making it sound flat across all frequencies. There is no true grey noise because all our ears are different and can be impacted by age and any hearing damage. Grey noise might not be perfect but it’s close.

What about other broadband timbres?

If you prefer non-computer-generated sounds, then nature sounds could be more appropriate for you. As previously discussed rain sounds, or other environment sounds can mask noxious background sounds.

Do you want to listen to noise or environmental sounds for masking?

The Can’t Sleep App includes grey noise and nature recordings such as rain, wind, waterfall, crickets, thunder, fire and many others, but masking is only beneficial when you have unpleasant sounds to hide. The Can’t Sleep App includes music designed to help you fall asleep faster and wake up feeling fresh. The app launches on the 29th of May 2018 and if you sign up early you will get free access to the app in its entirety.

Interested in sleeping better?