Dynamic range for audio refers to the difference between the quietest and loudest sounds an audio system can produce with nuance and no distortion. In this article, we will take a close look at this concept and explain why dynamic range is important for making your home theater immersive.
Dynamics are a fundamental element in movies and music alongside components like plot, acting, lyrics, and cinematography, that contribute to the enjoyment and captivation of the audience. A film or song that has noticeable fluctuations in intensity is almost always more captivating than one that maintains a consistent level of intensity throughout.
However, if the dynamic range is too large it can break that immersion and degrade the experience. For instance, if a movie has a very wide dynamic range, it can be challenging to hear the quieter dialogue without the action scenes becoming uncomfortably loud.
Take the movie Tenet as an example of a broad dynamic range, where the difference in sound levels between the action and dialogue is so extreme that most home systems struggle to find a balance. It then becomes difficult to hear the dialogue without the action scenes being ear-splittingly loud; however, this was a decision made by the director to only focus on mixing for larger theaters and not home mixes.
On the other hand, if the difference between soft and loud sounds is too small, the film or music may feel unexciting or even overwhelming to our senses, especially when listened to at higher volumes.
The ideal audio dynamic range is balanced and natural, where you can hear all the nuances and variations in the sound without compromising your comfort or your equipment.
Another role that the dynamic range of the audio holds is how it is used to tell stories and emotion. For instance, when crafting a suspenseful sequence, directors deliberately avoid maintaining a constant level of tension. Doing so would result in monotony rather than gripping the audience’s attention. The nuanced dynamics between each moment are what infuse the sequence with suspense and cinematic impact. Similarly, actors often transition from louder to softer emotions as they move from one scene to another or even within individual lines, thereby enriching their performances with depth and subtlety.
Therefore, when we create and set up our home theaters, our goal is to accurately recreate what the directors and artists intended. We want to capture the original experience and bring it to life without losing any of the emotional impact.
Now let’s look at the technical details of what affects the dynamic range of your system.
The audio dynamic range is measured in decibels (dB) of the loudest audio peaks to the quietest sound, and is affected by multiple factors in your audio setup.
Dynamic Range of Human Hearing
First, let’s talk about our biological limits. Our ability to perceive different frequencies varies, which means the dynamic range of our hearing also fluctuates depending on the frequencies being played. This makes it more challenging to determine the exact limit of the dynamic range for human hearing.
When it comes to intensity, our ears have a dynamic range that spans from 0dB (threshold) to approximately 120-130dB for the frequencies we are most sensitive to, which are typically between 2kHz and 3kHz. However, as we move away from these frequencies, the dynamic range of our hearing decreases.
In real-life environments, we are rarely exposed to sounds quieter than 30dB. This limit is called the noise floor of the environment. For reference, 30dB is about as loud as a whisper and is considered a good noise floor in a home theater. Therefore, the lower limit of 0dB for our dynamic range needs to be adjusted to match our noise floor. Taking this into account, our effective dynamic range for our senses is typically reduced to around 90dB for our most sensitive frequencies.
It is important to note that higher sustained intensities above 90dB can be harmful to the inner ear, with irreversible damage occurring at levels above 120dB.
Dynamic Range of Audio Equipment
The dynamic range of your audio equipment is a measure of its ability to play sound without distortion. Typically, the limitation lies on the louder end, as the volume increases, requiring your equipment to work harder to reproduce the audio at the higher intensities.
To calculate the dynamic range of equipment, we compare the loudest sound it can produce without distortion to the quietest sound before unwanted noise becomes noticeable. A larger difference indicates a larger dynamic range, providing more headroom for handling various sound levels without distortion.
When the signal volume (gray line in image below) exceeds the equipment’s threshold indicating that it is reaching it limits (+40, -40 horizontal lines), distortion and loss of detail can occur as the system struggles to accurately reproduce the sound. The sound becomes clipped at the limits (red line in image below), resulting in a squaring of the audio wave. This clipping has the effect of reducing the dynamic range and also creating distortion. Conversely, on the low side, random electrical noise becomes audible, also known as the noise floor, which can obscure the details in the mix.
Dynamic Range of Content
Audio dynamic range is also content dependent. Meaning that different types of content have different levels of dynamic range encoded in them. For example, music typically has a lower dynamic range than movies or games, because music is usually compressed to make it louder and more consistent across different devices and platforms. Movies and games typically have a higher dynamic range than music, because they are designed to create immersive and realistic sound effects that vary from quiet to loud.
The content’s dynamic range is also affected by its mastering process, as we talked about with Tenet above. Mastering is the final stage of audio production, where the audio signal is processed to optimize its quality and compatibility for different devices and platforms. Mastering can enhance or reduce the dynamic range of the content depending on various factors, such as artistic preferences, genre conventions, or technical limitations.
The source device also has its own maximum dynamic range, determined by its bit depth. Bit depth refers to the number of bits used to represent each sample of an audio signal. A higher bit depth allows for more possible values in each sample, resulting in a greater dynamic range. For instance, streaming platforms like Netflix typically have a bit depth of 24 bits, enabling a maximum dynamic range of 144dB, which is well beyond what we can perceive. On the other hand, a CD has a bit depth of 16 bits, corresponding to a dynamic range of 90dB, which is at the upper limit of our hearing range.
In the digital age, it can be argued that most forms of media can meet or even exceed our natural dynamic range, and therefore, the limit for the dynamic range falls on the other factors stated above.
Putting It All Together
Based on the points discussed above, we can conclude that it is important to have a dynamic range that matches the content we’re listening to at our max preferred volume level. This allows us to experience the full impact and emotion intended by the creator. However, since we listen to different types of content with varying dynamic ranges and at different volume levels, it becomes challenging to recommend a single dynamic range number. Moreover, the range is also frequency dependent as we learned that we do not perceive all frequencies the same.
However, for a rough estimate, if we know the maximum and average volume level we set for our system and determine the largest dynamic range content we consume, we can then add and subtract these numbers to ensure clean audio output. It is also a good idea to leave a 3dB headroom at the high end of the range to ensure accurate sound reproduction.
For example, the loudest I would set my system to is around -13dB on the reference scale, which corresponds to an average program level of 72dB absolute. The content with the largest dynamic range that I listen to is movies, which can have swings of 20-30dB in each direction. So my range, accounting for the headroom, would be from 42dB to 105dB. However, these numbers may change slightly because I don’t always listen at -13dB. My average listening level is -18dB (67dB), so my average range would be from 38dB to 98dB. Therefore, combining these two ranges, I want to aim for a dynamic range from 38dB to 105dB. It is important to note that these numbers assume that we perceive all frequencies equally, which is not the case.
To truly understand the required dynamic range, we would need to consider and calculate the perception of each frequency and create a dynamic range curve to aim for, but that’s beyond the scope of this discussion.
If you would like additional help understanding the dynamic range of your system or any other home theater related topic, feel free to leave a comment below or book some time with us at Simple Home Cinema. See more about it here, or by clicking below.