Decibels Decoded: A Guide to Understanding Loudness

Willem Grobler | February 5, 2024 10:39 pm

In our everyday lives, loudness is more than just a measure of sound intensity; it’s an intricate perception shaped by physical, psychological, and environmental factors. In this article, we explore how decibels interact with the human auditory system to create the sensation of loudness.

This phenomenon goes beyond mere volume levels; it encompasses how our ears and brains interpret sound waves, the context in which we hear them, and even the emotional responses they evoke. We hope to provide some insight into how and why certain sounds appear louder than others and how this understanding can impact your decisions when buying a speaker, headphones, or earbuds.

The Human Perception of Loudness

Putting a value to loudness as humans hear it is much more complex than the sound pressure level (SPL) numbers published by manufacturers, measured in decibels (dB) with acoustical instruments. A decibel is an objective logarithmic measuring unit of sound pressure.

“Loudness”, or our perception of loudness and “volume” are psychoacoustical terms.  It describes subjective sound-sensations, and measuring them is fraught with ambiguity.

That does not mean the decibel specs on your speaker are completely useless, though. It simply means that understanding their impact on how loud your ear will perceive the speaker to be is a lot more complex than thinking a 100 dB speaker is twice as loud as a 50 dB speaker.  Not even close!

Our perception of how loud a speaker sounds doubles every time you increase the output by 10 dB.  A 100 dB speaker will sound twice as loud to your ear as a 90 dB speaker.  A 120 dB speaker will sound four times as loud as a 100 dB speaker and eight times louder than a 90 dB speaker!

What Makes a Speaker Loud?

The intensity of a given sound is measured in decibels (dB), but there are various ways to drive up the volume of a speaker within the speaker’s design. When a signal has made it to your speaker, it has been converted from a digital signal to an analog electrical signal. Afterward, the electrical signal is translated into mechanical energy (i.e., the woofers and tweeters moving) and then into acoustical energy once the air starts moving. The magic happens when that wiggling air vibrates our eardrums, and we hear that as sound!

So, how do speakers make more air vibrate? Well, there’s a reason you probably assume that the biggest Bluetooth speakers are the loudest. Increasing the size of a speaker is the simplest way to make it louder because a larger speaker can move more air and thus create more volume.

Another way to increase the perceived volume of speakers is by getting a speaker with a better frequency response. Frequency response is a measure of a speaker’s accuracy. It measures how accurate the sound waves the speaker produces are compared to the electrical signal the speaker receives. This is why a small Bluetooth speaker sounds better than laptop speakers because it is slightly bigger and has a better frequency response than the speakers on your laptop!

What is the Relationship Between Power (W) and Volume (dB)?

In the speaker world, power (measured in watts) is electrical power provided by an amplifier, which is usually a separate piece of equipment from the speakers. Decibels (dB) are units used to measure a sound’s intensity on a logarithmic scale. Volume is subjective; loud noise to one person may be quiet to another, so the decibel scale compares sounds relative to other sounds. Decibels show the ratio between different signal levels, whereas watts are an exact measurement of an electrical circuit’s rate of energy transference.

The relationship between watts and decibels is confusing at first because watts are an exact unit and decibels are a relative unit.

A rule of thumb is that doubling your power will get you an increase of 3 dB. Increasing the power ten times will increase your dB by +10 and only double the perceived loudness. Adding power is inefficient for increasing volume due to the dynamic driver speaker’s inherent design flaws.

This is why the loudest speaker in the world requires enormous amounts of power for incremental volume gains. This relationship is a great way to illustrate that speakers are some of the most inefficient products we commonly use today since only 1% of power turns into sound. Most of the power sent to speakers turns into heat!

What are A-Weighted Decibels? (dBa)

A-weighted decibels (dBa) measure sound pressure levels just like regular decibels but adjusted to account for relative loudness factors as perceived by human ears. The relationship between dB and dBa is illustrated by a specific graph where a curve called the ‘equal-loudness contour’ is projected on top of a typical logarithmic dB scale. Essentially, A-weighting is like leveling the playing field for decibels.

The human ear hears different frequencies differently because our ears evolved to accentuate and ignore different sounds necessary for survival. This means that to hear a very low-pitched frequency, like 20Hz, at the same perceived loudness as a noise of 1kHz (1000Hz), you would need to increase the dB by +50. Again, this is all due to the natural way our ears perceive sounds.

If that confused you, try to think of it like this. Very high and low-pitched noises sound quieter, but they aren’t really. A-weighting is simply the process of accounting for that relative change in perceived volume. A-weighted decibels (dBa) are just decibels (dB) adjusted to reflect perceived loudness.

How Loud is Too Loud?

What Influences How Loud a Speaker Sounds?

Ignoring the acoustic properties of the room where your speakers are located can pretty much ignore all the great (and expensive) features that made your speakers appeal to you when you first picked them out. If your speakers have a great frequency response, but your room is filled with hard surfaces that reflect noise, your sound quality may still be muddy. There are, however, quite a few ways you can improve your speaker’s sound quality right now.

The most obvious change you can make to your speaker setup to enhance your sound quality and perceived loudness is to tweak your speaker arrangement. Sit in the same spot, play the same song or clip from a film, and make small, measured adjustments to the location of your speakers. Be sure to get creative! All rooms are different, so take notes on increases and decreases in quality; you will be surprised how much a small adjustment can change your audio experience.

Another way to change how your sound system sounds is to soften your room’s décor. Place throw rugs where sounds bounce off hard floors, or add a few canvas paintings to your walls. Both of these things will dampen sounds, meaning the sound from your speakers won’t bounce off hard surfaces and clash with the priority signals from your speakers.

Relative Loudness Compared

The easiest way to explain decibels is to explain how sounds compare to other sounds. Human beings can hear very weak sounds at ~10 dB up to the pain threshold at ~140 dB.

Starting at the low end, let’s list a few quiet noises you may hear in your day-to-day life:

  • 0-5 dB – Recording studio
  • 10 dB – Computer running in a quiet bedroom
  • 30 dB – Whispering
  • 40 dB – Refrigerator
  • 60 dB – Living room with the TV on

Next, some reasonable volumes you have probably encountered recently:

  • 70 dB – Shower
  • 80 dB – City traffic
  • 90 dB – Helicopter overhead

Finally, common sounds that can damage your ears if you aren’t careful:

  • 120 dB – Sirens
  • 130 dB – Plane taking off
  • 140 dB – Fireworks (Warning: Threshold of pain!)

Here’s a more visual comparison of these decibel levels on a graph:

It’s important to note that as a rule of thumb you should wear protection for your ears when around any sounds above 85 dB, especially if it’s for an extended period. Protect your hearing if you want to spend your whole life listening to great speakers.

How Can I Test How Loud My Speakers Are?

Manufacturers measure the loudness of their speakers by measuring the SPL (sound pressure level) and dB of their speakers with a microphone one meter away. This is usually represented as ‘dBs @ 1W/1m’ or ‘dBs @ 2.83V/m’ respectively.

The best way to measure the loudness of your speakers at home is to place a microphone with a dB meter connected to it 1 meter in front of the speakers, just as the manufacturer did before the speakers were sent out to stores. This time, however, you can feel free to change volume settings on your amp and take note on your phone or notepad of what dB level is achieved at the amplitude levels on your amplifier. This will be the easiest way to test the loudness of your sound system at home.

If you don’t have access to high-quality audio equipment like dB meters, don’t fret; you can get an app on the app store for a dB meter; check the reviews in the app’s description before downloading to see each dB meter app’s reliability and accuracy. Standalone hardware dB meters usually cost anywhere from $50 to $300, so the app can get you a lot of functionality at a much lower price point.

How Can I Prevent Hearing Damage?

Always be aware of the irreversible damage that can be done to your ears when listening to loud (90+ dB) noises, especially for extended periods of time. When using headphones, it is common knowledge to never listen at max volume, but with speakers’ people have differing opinions about what levels are comfortable for them.

Many speaker systems have great frequency response and don’t require extreme volumes to hear details in the audio signals you are listening to. When listening at louder than normal volumes in the cases of concerts, festivals, and parties, it is always wise to wear earplugs to protect your ears. The best policy for protecting your hearing when listening to loud music is to be aware and conscious of the dangers of listening to extreme volumes.

In the case of audio, you can have too much of a good thing, so protect your hearing now to enjoy more time with your favorite music before your ears are too damaged to hear those timeless favorites you once enjoyed.

Wear earplugs in loud public settings like concerts or construction sites, and at home, don’t crank that knob all the way!

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Author: Willem Grobler

Willem is an audio enthusiast who's office and home is cluttered with Bluetooth speakers and headphones. He appreciates honest speakers which delivers on their design and marketing promises. His go to speaker when traveling with his family is a JBL Flip 6, but as he loves the outdoors makes no secret of his love for the Turtlebox Gen 2.

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