Loudness, Volume, Level, Amplitude

🎯 Learning Objectives:

In this topic we will try to answer the question of how loud a sound is. As we dive through this module, we will quickly find out that answering this question is not as easy or intuitive as it seems. But before delving into the concept of measure of levels and the human perception of loudness, we will take a look at the obscure and often and often overloaded terminology used in acoustics to represent the general concept of how loud a sound is. We will learn about loudness, volume, level, amplitude, gain and drive.

📘 In this topic we will talk all about loudness and levels and all the different ways that music and audio was perceived and measured. But before we address any of that we need to talk about the obscure and often overloaded terminology used in acoustics to represent the general concept of how loud a sound is.
So below is a list of the terms:

1. Loudness
2. Level
3. Volume
4. Amplitude
5. Gain
6. Drive

⭐ Is there a difference between them? YES
⭐ Are they interchangeable? NO
⭐ Is the difference between them important for a regular person to understand? Probably NOT
⭐ Is the difference between them important for an audio engineer or programmer to understand? Absolutely YES

The question how loud is a sound is not an easy question to answer as you will soon find out. But the language used to represent this concept can be contained and simplified, so the discussion becomes easier.
These acoustical terms can be broadly categorized as either being

What does that mean?

• Objectively measuring something means that you are quantifying the result as a mathematical formula or a number and you can repeat the measurements under the same conditions any number of times and you should end up getting the same result every time.
• Subjective perception is a lot more hairy. It is how an individual can perceive something and it is more a qualitative measure than something that can be quantified into a number.

You might have heard of these terms in the context of music that a sound is either

• Bumi or punchy
• Muddy or warm
• Airy or harsh
• Bright or dark
• Loud or quiet

What might appear a loud to you might not for another person. Sure a certain trend in measurement can result in a subjective perception to appear. For example boosting frequency's at around a 100 Hz to 400 Hz could mean a warm sounding track. But if it is overdone this range of frequencies can cause the track to sound muddy.

⭐ Who is to judge if the track is muddy or not: YOU ARE

You are the subject who decides adding three decibels (3 dB) of gain on a band further at 200 Hz is muddy or not. When another person is subjected to the same set of objective parameters applied he might find it completely different.

⭐ Loudness and volume or subjective attributes of audio

Loudness:

Loudness can be thought of as an auditory sensation where sounds can be ordered on a scale from quiet to loud. It does not just depend on the physical factors such as intensity of the pressure waves reaching your ears, but it also depends on physiological factors like how your ears are designed and the natural resonance produced within the boundary of the year. Even psychological factors like how your brain colors the perception of loudness for different frequencies matter as well.

⭐ Physical Factor: Such as air pressure

⭐ Physiological Factor:

⭐ Psychological Factors:

Volume:

Volume is quite similar to loudness but the term is usually used contextually with the final loudness you can achieve from an amplifier be it analog or digital. You would have come across volume controls on your radios or speakers or guitar amplifiers with values ranging from 0 to 10.

You might ask if you can associate volume with a number.
⭐ Does that not mean that it's an objective measure?
⭐ What does a volume setting of 4 mean when comparing a tiny desk speaker to a 100 Watt guitar amplifier?

It does not translate the same loudness, it is just a convenience measure for consumers.

Gain:

Gain is an objective measurement and used in the context of electronics as a measure of the ability of an amplifier circuit to increase or decrease the electrical power of the input signal. Gain is a ratio between the electrical power of the signal at the output stage to the electrical power of the signal at the input stage. If the electrical power of the output signal is higher after amplification then the gain is positive and if it is lower the gain is negative.

You might have come across game controls on amplifiers or audio interfaces. If you look at a guitar amp for example you have both the gain knob and a volume knob increasing either knobs would increase the loudness of the signal. But what happens underneath the hood is that a guitar amplifier is made up of a preamplifier stage which boosts the weak signal from the input line-in and a power amplifier stage which drives a loud speaker. In short we can say,
⭐ The gain knob is used to control the gain parameter of the preamplifier stage.
⭐ The the volume knob is used to control the gain parameter of the power amplifier stage.

You can imagine then whatever comes out of the preamplifier stage is then blindly amplified by the power amplifier and the power amplifier determines the final loudness of the signal. There may be cases where you can increase the gain of a preamplifier to the point where the signal starts clipping and start distorting. The preamplifier stage can be over driven to produce a warm subtle distortion or a harsh fuzzy distortion and both of which can be used artistically. The power amplifier is just used to boost up the loudness of the signal from the output of the preamplifier stage, whatever the state of the signal might be in.

Drive:

Drive is a term that can be used as a synonym for gain in the context of amplifiers. They are both the same.

Amplitude:

Amplitude and level can be interchangeably used. Amplitude refers to the instantaneous value of a signal over time. We will see a few different ways the amplitude or level of a signal can be measured and its implications with respect to the loudness of the sound produced. Amplitude as a term is pretty broad and can be used in several different contexts. It can be used for measuring the strength of pressure waves in the physical world. When these pressure waves are captured by a microphone and converted into electrical signals we can measure the amplitude of the voltage or current pass through these electrical cables. Even when the signal is converted into the digital domain we can measure the amplitude of the sample the values of the digitized signal. We can measure the peak value, the peak to peak value or the root mean squared or the average magnitude value of signal and all these measurements are done on the decibel scale.

Generally, as the level of the signal increases its perceived loudness increases as well. It is not necessarily true that two different signals with the same amplitude can be perceived as having the same loudness.
All right that covers all the terms used in this topic. Let us put them all in a single sentence:

🏅 As I turned the volume knob down, I reduced the gain of the amplifier, reducing the amplitude or level of the signal, which resulted in the loudness of the sound being lowered.

❗ Remarks:
If you are new to this topics there is doubt that it is confusing with some terms being redundant and ambiguous at times. It takes a while to use the right term in the right context. But as you understand it better you will understand that they are fundamentally different concepts with their own areas of study.

📝 Key Takeaways: Loudness, Volume, Gain, and Amplitude

• 📌 Summary

  Turning down the volume reduces amplifier gain, lowering the signal amplitude, which decreases perceived loudness.

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