The Deciblog – How Loud is a Guitar in Decibels & other must-know trivia

We love our loud guitars and hanker for crunchy amps right from our dilettante days. Yet, when it comes to the facts, there is a lot of ambiguity surrounding wattage, speaker efficiency, loudness, and decibels.

These terms not only demand a lot of curiosity but they are also riddled with misnomers and subject to false myths that are plastered all over the internet. So, we’ve thrown in everything that a musician ought to know coupled with some quirky facts and interesting trivia about noise, amplification, and sound.

dB and Decibels: What does it mean and measure?

Bel is a unit used to measure sound like we use meter or feet to measure distance. It is named after Alexander Graham Bell, the guy who invented the telephone (the kind that we don’t use anymore). So – A “deci” Bel is one-tenth of that unit because deci means one-tenth.

A decibel (dB) = 1/10 of a Bel (a unit of sound)

Sound is measured in decibels – so dB is the most common unit to measure loudness. It measures the amplitude of a sound wave – the highest extent of a vibration from a position of equilibrium. In simple words, it’s the pressure or forcefulness of the sound or the “intensity” of sound that is represented in dB.

The human ear is sensitive to sounds ranging from 0 dB (eerie silence) to 130 dB (painfully loud). The lower end of the spectrum makes you feel uncomfortable and the higher end of it hurts. Studies have shown that the human ear can only tolerate 130 to 140 decibels. At 150 decibels, you are going to burst an eardrum and 180-200 dB can even prove fatal. Considering that a lawnmower is about 100 dB, we could claim we flirt with death every day.

A decibel scale is logarithmic, not linear. So, to the human ear, an increase of 10 dB will make a sound seem twice as loud, and increasing 20 dB will make it seem 4 times louder and so on.

How do you measure decibels (dB)?

You can get a dB meter, also known as a sound level meter. It’s available online or at specialty stores and is used to accurately measure levels of sound. You can also download Android and iOS dB meter apps from their app stores.    

How loud is an acoustic guitar in decibels?

A rough estimate would be 80 dB when you are trying to strum it as loudly as possible. There is no ‘official’ answer and this can vary due to numerous parameters. Although, technically speaking, you’d have to smash the guitar into a wall or floor to generate the ‘loudest sound’. Don’t damage your wallet and your eardrum.

Larger guitar bodies have a louder output in the low-frequency range, but they do not have more volume. These ‘lows’ spread or discharge in all directions equally, so they can be heard well, especially by the person playing the guitar. At higher frequencies, the sound of the guitar becomes directional. It travels off the top and out of the soundhole towards the audience.

For this reason, we perceive guitars with large body shapes to be ‘louder’ but you will often hear smaller ones and feel that they ‘project’ better. Of course, the angle at which you stand and the distance play a big role in all this.

How loud is an electric guitar in decibels?

Huh? An electric guitar is not loud at all – that’s why you need amplification.

Okay, fine! How loud is a guitar amp in decibels?

Most guitar amps are around 115 dB if you’re located a meter (or 3.28 feet) away from the speaker/cabinet. However, if you’re standing right next to the speaker of a fully distorted 700W head with a 4×12 cabinet, it’s about 135 dB. That’s awfully close to the “150 dB” it takes to burst an eardrum. Let us not forget the impact of effects pedals and compression. At the same volume, a clean signal will sound quieter than a signal with compression, gain, and distortion.

Deep Purple, thanks to the Live Concert at London’s Rainbow Theatre in 1972, holds the Guinness Book of Record’s title for “the world’s loudest band” – a staggering 117 decibels

Speaker Sensitivity, Speaker Efficiency, and Guitar Amplification

First off, the correct term for speaker efficiency is speaker sensitivity but over the years, the two terms have become interchangeable. For the sake of simplicity, we will stick with speaker sensitivity. 

What does speaker sensitivity mean?

Speaker sensitivity is a measure used to determine how much power is needed to drive or operate a speaker. How much sound output do you get from an amplifier when you have 1-watt of power input? Yup, that’s what we call speaker sensitivity or speaker efficiency.

The speaker sensitivity is directly proportional to the loudness and it’s denoted as “sensitivity rating” in dB (decibels). Thus, the higher the sensitivity rating, the louder the speaker will be. Most speakers we encounter on a regular basis range from 97 dB to 100 dB, but a fair amount of them fall below and above this.

How do they test or measure speaker efficiency for a guitar amplifier?

Generally, they deliver 1-watt of power (input) to a speaker and use a microphone placed one meter away from it. The microphone measures the ‘resulting volume’ using a decibel level meter. This gives you an output level. Now we have the input level (1-watt) and the output level and this is used to calculate the speaker’s efficiency rating. 

What is “gain” on a guitar amplifier?

On guitar amps, gain is the strength (level) of the signal sent through the preamp. It is also called “drive” because the gain control determines the level of distortion in your tone. This is not dependent on the master volume level.

Guitar amps, Wattage, and Volume –Watt not to do!

Watt (W) is named after a Scottish inventor named James Watt. It is a unit to measure energy – the energy output of an amplifier in our context. Most speakers or guitar amplifiers/cabinets are “rated” for the watts they can handle i.e. 30W or 100W.

An amp head that produces more watts than the ‘watt rating’ of a cabinet can result in a blow out that can damage the speaker.

Loudness is not represented by an amplifier’s power rating or wattage. Watts measure the energy and dB measure the sound. 10 watts does not mean 10 dB of volume. Instead, to get a good idea about an amplifier power, you should look at a) the speaker sensitivity, and b) the capacity to handle volume peaks.

Amp manufacturers are notorious in the way they rate their amplifiers. Most 100-watt amps are rated “100watt max clean” but some amps are rated “100-watts full out” but that actually means 77watts of max clean.

For instance – a Celestion G12T-75 is 75W and is most commonly used in certain Marshall cabs that are rated 97 decibels. The Celestion V30 is 60W and it is used in other Marshall cabs that are rated 100 dB. Clearly, a Celestion Vintage 30 (60 watts) is 3 dB louder than the Celestion G12T (75 watts).

This should help clear the common misconception that “wattage = volume” – it is simply not true. A 25-watt guitar amp with a Celestion V30 speaker can be as loud as a 50-watt amp with a Celestion G12T. Speaker Wattage has nothing to do with speaker efficiency – you will find many speakers with different wattages that still have the same efficiency.

15 watts, 30 watts, and 100 watts amps: Which is loud enough to gig?

Wattage has very little to do with volume, but to answer the question – a 15-watt head like the Fender Super Champ x2 is loud enough for rehearsals, home-recording, and small venue gigs. However, it might be lacking when it comes to a full band setup and medium to big-sized venues. You will also struggle to sound clean at high volumes.

A 30 watts tube amp like the Orange TH30 is sufficient for most gigs unless you are playing huge concerts. For the bigger venues, you can mic it up. Remember, when you go from 30W to 300W – that is just a 10 dB spike in volume. However, at 30W you still won’t find ultra-clean tones at high volumes.

A 100-watt tube head like the Marshall JCM800 is loud. It might be too loud for most applications that don’t involve a big stage. Frankly, 50 watts of tube OR solid-state is loud enough for almost all applications unless you are a touring professional musician.  

Moral of the Story? Get earplugs and USE them.

You should also know that continuous exposure to sound over 85 dB could cause damage or hearing loss. Our entire editorial team agrees that hearing protection is really underrated and underappreciated. It’s imperative for drummers to use isolation headphones like Vic Firth DB22 and musicians to get a reliable pair of earplugs like Decibullz

Most guitar amps are capable of 115 dB when you are roughly one meter away from the speaker. They damage your ears slowly and innocuously, it is a long and painless decline – an unfortunate truth is you rarely notice it until it is too late.

An airplane engine (jet engine) is close to 120 dB. The people who work in and around that noise are subject to loud sounds for long periods of time (and/or frequently). If the airport runway crew is wearing protective earmuffs, clearly there is a need for it.

Even with high-quality earplugs, you are only reducing about 30 dB, which is not enough if you are being exposed to 115 dB for a considerable amount of time. It may not even help if you buy cheap earplugs that are leaking.  A good way to know if you are damaging your hearing or eardrums is to just pay attention to how you feel. Damage usually involves a strangely diminished listening capacity for 20 to 30 minutes and/or a constant ringing in your ear.

Final Thoughts    

I hope this article brings you up to speed with most of the jargon/terminology and must-know facts about sound and guitar amplification. Knowledge is the greatest power, especially when it comes to showboating on the forums. If you enjoyed this article, share it – loud and proud – with your friends.

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