You might notice when you’re playing in a band that certain sounds carry better than others. You’ll often hear the high notes standing out over the rest of the band. On the other hand, if you’re living near someone who plays really loud music, the bit you usually hear is the bass. I’ve often wondered whether the pitch of the note has an impact on its volume so I decided to look into it in more detail.
Lower frequency sounds are able to propagate further through materials, so over long distances, you will usually hear these better. At shorter distances, higher frequencies are usually heard the loudest because of the way the human ear is designed.
There’s a lot of physics in how we hear musical notes. When we listen to music, we notice some parts are louder than others. This can be the players controlling their volume but it can also be related to the ear’s ability to perceive different frequencies (pitches). I’ll talk a bit about how the ear detects different pitches and also about how sound wave propagate through different materials. This should give some insight into why we hear different pitches at different volumes.
Scientific terms
I’ll be using some scientific terms in this post to explain the concepts I’m talking about. I’ll define them all here so there is something to refer back to if you’re struggling to follow.
- Sound wave – when you play a note, a wave of sound travels through the air to your ear
- Frequency – the number of repeats of a sound wave that occur in a certain time (particular frequencies correspond to particular pitches)
- Amplitude – the amplitude of a way is how big the wave is and equates to volume
- Attenuation – the reduction in intensity of a (sound) wave as it passes through materials
I’ll also talk a bit about how the human ear perceives sound. I won’t go into the science of this in too much detail here, but I talk about it a lot more in one of my other articles: https://woodwindgeek.com/how-does-tuning-between-instruments-affect-volume/. If you’re struggling to understand some of the stuff I’m saying about the ear, or you’re just interested to know more about it, have a look here.
Does higher frequency mean higher volume?
If you’re a musician, you’ve probably thought at some point that high notes always sound way too loud. It’s definitely the case that they can be heard better by the people in and around the band. The question is whether higher pitches actually mean louder volume or whether something else is happening.
It’s definitely the case in plenty of amateur bands that the higher notes will actually be played louder. On wind instruments, high notes are typically harder to play than low notes, so the players will be forcing more air through the instruments to get them to sound properly. This will often lead to the higher pitches overpowering the lower pitches. However, even when the musicians are working hard to control their volume, the higher notes still seem to carry better.
There is a scientific reason behind this perceived increase in volume for higher notes. It’s to do with how the human ear responds to different frequencies. You can play two notes that have waves with the same amplitude, but if one is a lower frequency than the other, the human ear does not hear it as intensely. This relates to the number of receptors that get excited in your ear when sound waves arrive in your cochlea.
The ear is, by design, more sensitive to higher frequencies than lower frequencies. This is thought to be because babies have high pitched voices, as do females, and it was necessary for a baby to pick out the sound of their mum’s voice, and vice versa. This then explains why higher instrument can carry more over quite short distances.
Why can I always hear bass sounds really loudly?
Now that I’ve talked about why high frequencies sound louder, it seems to make even less sense why bass sounds would always filter through. There are a couple of reasons for this. One reason is that musicians often compensate for the fact that lower frequencies tend to be quieter, by turning the volume of the low instruments up much louder. But even then, sometimes you can only hear the bass of the music and nothing else, so different frequencies definitely don’t carrying evenly.
The reason for this is that different frequencies are attenuated different amounts by materials they pass through. While you might have to turn low frequencies up much louder to hear them at the same volume as high frequencies when you’re in the same room, once the sound waves have to travel through walls, the situation changes completely.
We now need to consider attenuation of sound waves. The frequency of sound waves affects their ability to propagate through certain materials. When a sound wave is “pushed” through a material, some amount of energy will be lost as heat. The further the sound wave propagates, the more of it will be lost to the material it’s passing through. Different frequencies are affected by different amounts.
It turns out that lower frequency waves can propagate better through materials, because they travel more slowly. Faster waves create more heat and therefore are more lossy. Similarly, different frequency waves reflect better from different materials. The usual materials we hear sound propagate through (for houses etc.) tend to reflect higher frequencies better than lower frequencies. More low frequencies then pass through and can be heard more clearly outside the room.
Summary
To sum up this article, there is a relationship between frequency and perceived volume, but not frequency and absolute volume. The human ear is more sensitive to high frequencies than low frequencies so when you play higher notes, they will be heard over the lower notes, assuming you’re within the same open space.
If there is something between you and the sound, there will be some amount of attenuation. In general, high frequency notes will be blocked better than low frequencies because of their shorter wavelength and faster speed. This leads to higher pitches being lost and lower pitches propagating a lot more easily. This is why when you hear a neighbour’s music, it’s usually the bass sound that is dominant.