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Why are we talking about dB now?
In audio development, there are always situations where you need to deal with sound volume, signal level, and noise effects numerically. Many design documents, datasheets, and measurement results are written using the dB (decibels) unit. However, while you may understand the dB formula, you might not fully grasp the underlying principles behind its use.
This article focuses on the "concept of units" in audio development, specifically addressing questions such as "why is dB used as a unit?" and "what becomes easier to understand when using dB?". We will examine the role of dB in audio development through specific perspectives related to design and evaluation, such as gain, noise, and dynamic range.
In audio development, "raw numerical values" are difficult to work with.
In audio development, quantities such as signal levels and noise are dealt with numerically, but simply considering them as magnitudes can make comparison and evaluation difficult. In actual design and evaluation settings, understanding the relationships between values is more important than understanding the values themselves.
Audio signals have a very wide range of capabilities.
Signals related to sound have the characteristic of having an extremely wide range. It is not uncommon to handle values of different orders of magnitude simultaneously, from very small noise levels to the maximum signal levels. In such an environment, it becomes difficult to intuitively grasp the differences and relationships between values by simply listing the numbers. In particular, when very small and very large values are mixed together, simple numerical representations tend to be difficult to compare.
In development, it's necessary to look for "differences" and "margins."
In audio development, it's important not only to understand the magnitude of the numerical values themselves, but also to understand the relationships between those values.
For example, evaluations often focus on "how different" the signal is, such as how much it's amplified, the magnitude of the noise relative to the signal, or how much headroom there is. In such situations, it's necessary to consider the differences and ratios, rather than simply comparing the values directly.
The concept of the dB (decibel) unit
dB is a unit that represents a "ratio," not "magnitude."
The dB (decibel) is not a unit that represents the magnitude of a value itself, but rather a unit that represents the "ratio" of how much something has changed relative to a reference value. Therefore, it can express relative relationships, such as how much larger or smaller something is, rather than its absolute magnitude.
What are the advantages of expressing things logarithmically?
dB is a unit expressed using logarithms.
This allows us to organize even very large or very small differences into a manageable numerical range. Furthermore, even when multiple amplifications or attenuations occur consecutively, their effects can be treated as additive, making it easier to grasp the overall relationship concisely. In this way, using logarithmic representation makes it possible to organize the wide range of values and the relationships involving multiple elements that are dealt with in audio development without difficulty.
Three situations in audio development where dB appears
Gain: How to understand the cumulative effect of amplification.
In audio circuits and DSP processing, signals undergo amplification and attenuation as they pass through multiple stages. Gain here refers to the increase in output relative to input, expressed as a ratio. For example, the signal may be amplified by a few dB at each stage, and these changes accumulate. In such cases, if the amplification amount is simply treated as a magnification factor, it becomes difficult to grasp the overall change.
On the other hand, expressing the changes in dB allows us to understand them by adding up the changes in each step, making it easier to organize the overall relationships.
Noise: How to evaluate small values
Noise is difficult to evaluate simply by its "smallness"; its relative magnitude to the signal—that is, its relationship as a ratio—is crucial. For example, even with the same noise level, noise may be more noticeable when the signal is small, while its impact may appear smaller when the signal is large.
Thus, to consider the effects of noise, it is necessary to understand it not in terms of its value itself, but in relation to the signal. What we want to look at here is not the absolute value of the noise, but the difference between the signal and the noise (how far apart they are). Expressing this difference in dB allows us to treat it as a single scale, and in design and measurement, it is common to describe the signal-to-noise ratio (SNR) in dB.
Dynamic range: How to define the range of what can be handled.
In audio signals, the range from the minimum to the maximum level that can be handled—that is, the dynamic range—is important. This indicates how well the signal can handle signals ranging from very small to very large without problems.
For example, if a very small signal is at the level of 0.000001, a large signal might be around 1. In this case, the difference in the signals that need to be handled is about 1,000,000 times. Thus, small signals are easily buried in noise, while large signals become distorted if they exceed their upper limit. Therefore, ensuring a range in which these can be handled appropriately is crucial in audio development. What we are looking at here is not the minimum or maximum value itself, but the difference between the two (how far apart they are).
However, if this difference is treated directly as a numerical value, it becomes a very large value, making it difficult to handle in comparisons and designs. Expressing it in dB allows such a large difference to be organized into a compact numerical value.
This makes it easier to compare and evaluate the width of signals. For this reason, dynamic range is generally described in dB in designs and specifications.
Summary: Why dB is always necessary in audio development.
This article has outlined how dB (decibels) are used in audio development, along with the underlying concepts. In audio signals, the range of values is very wide, and it's crucial to understand not only the values themselves, but also the differences and ratios between signals.
In actual development,
Gain: The change (ratio) of output relative to input.
• Noise: Its relative magnitude (relationship) to the signal.
• Dynamic range: The difference (width) between the minimum and maximum values.
As you can see, the common theme in all of these is how to interpret the relationships between values. If these are treated as numerical values as they are, they tend to have large differences in magnitude and complex relationships, making them difficult to handle in design and comparison. By using the concept of the dB unit, these relationships can be organized into a single scale, making comparison and evaluation easier. Therefore, dB is not merely a unit or a tool for calculations, but is used in audio development as a fundamental concept for appropriately capturing signals.
Related Information
As we have seen, in audio development, characteristics such as signal level, noise, and dynamic range are considered and evaluated using the dB scale. When actually performing such signal level adjustments and optimizations, utilizing an audio development platform is effective.
DSP Concepts' audio development platform, "Audio Weaver," provides an environment where you can intuitively design and verify sound-related processes such as gain adjustment and noise reduction using a GUI.
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