Is 24-Bit FLAC Better Than 16-Bit?

The bit depth of audio recordings is often cited as a marker of sound quality. So, does this mean that 24-bit FLAC is better than 16-bit?

24-bit FLAC is not audibly better than 16-bit. Increasing the bit depth from 16 to 24 does not produce a perceptible improvement in sound quality. While 24-bit FLAC converts more input audio data with greater accuracy than 16-bit, the human auditory system cannot perceive these sampling improvements.

Many music companies and streaming services enthusiastically depict 24-bit audio as the new gold standard of sound quality. There is an intuitive appeal to the claim that a FLAC (Free Lossless Audio Codec) file with a bit depth of 24 is superior to 16, but does this assertion hold in practice?

24-Bit FLAC Is Not Audibly Better Than 16-Bit FLAC

Comparing different bit depths of FLAC format (or any other format) is complex, involving multiple mathematical, auditory, and hardware-related variables. Due to this complexity, the marketing claim that 24-bit audio is superior to 16-bit is widely-accepted. In practice, however, 24-bit FLAC format is not audibly better than 16-bit.

Higher bit depth sampling performs better in certain technical respects. When compared with low bit depth audio, a high bit depth recording:

  • captures more of the input data,
  • reproduces the input waveforms more accurately (with higher fidelity),
  • creates less quantization noise.

Despite this enhanced sampling performance, the difference between 24-bit and 16-bit recordings is a mathematical abstraction with little relevance in real-life listening scenarios. In practice, the average person cannot differentiate between the sound of 24-bit versus 16-bit FLAC.

The reason 24-bit FLAC sounds indistinguishable from a 16-bit version is due to the limits of the human auditory system. While 24-bit FLAC sampling achieves higher resolution than 16-bit, this improvement occurs at frequencies and amplitudes beyond the threshold of peoples’ hearing abilities.

It is worth borrowing an analogy from Christopher Montgomery, the creator of the .ogg audio format. Montgomery compares 24-bit audio to a video that reproduces the entire light spectrum, including frequencies invisible to the human eye.

A Closer Look At 24-Bit And 16-Bit FLAC Audio

Understanding why 24-bit FLAC is not substantively better than 16-bit requires a closer examination of bit depth, quantization, dynamic range, and signal-to-noise ratio.

Bit Depth

Bit depth refers to the number of bits of audio data per sample. In simple terms, bit depth is the amount of information contained in every sample of an audio recording. More technically, bit depth is the possible number of amplitude values in each sample. 

Bit depth applies to pulse-code modulation (PCM) audio data. This uncompressed audio information is typically found on compact discs with a bit depth of 16 bits. 24-bit PCM audio is most commonly associated with Blu-ray and DVD-Audio discs. FLAC and its native container format are often used to encode and store PCM data.

Higher bit depth sampling produces a more precise digital approximation of an input waveform than audio recordings at lower bit depths. High bit depth audio also has a superior dynamic range and signal-to-noise ratio compared with low bit depth recordings.

It is critical to emphasize that these differences between high and low bit depth sampling are generally outside the scope of human auditory perception.

In addition, sound production methods like over-sampling, dithering, and noise-shaping can virtually eliminate differences between low and high bit depth audio outputs. 

The varying outcomes audio sampling at different bit depths achieves are due to the fundamental relationship between bit depth and quantization.

Quantization

Quantization is the conversion of a continually varying analog waveform into a sequence of digital samples, each consisting of specific numerical values.

There are always some discrepancies between the original analog signal and its binary representation. The process of quantization is never 100% accurate because it is impossible to reproduce an identical copy of an ever-changing sine waveform with ones and zeros.

Deviations between the analog waveform and the digital representation are corrected by adjusting or rounding the input signal up or down to the nearest potential value. The rounding procedure introduces quantization errors or noise.

As high bit depth audio sampling approximates the waveform at a finer, more accurate resolution, the resulting audio has less quantization noise than lower bit depth recordings. This provides the basis for claims that 24-bit audio produces superior playback quality to 16-bit recordings.

While 24-bit FLAC audio sampling has smaller quantization errors than 16-bit, this does not necessarily translate into audible improvements in sound quality.

In contemporary digital audio processing, the quantization errors that 16-bit sampling produces are imperceptible to most humans. So, while 24-bit audio quantizes input signals with fewer errors, this improvement manifests beyond the limits of human hearing abilities.

Signal-To-Noise Ratio And Dynamic Range

In comparison to 16-bit FLAC, 24-bit has a higher dynamic range and signal-to-noise (SNR) ratio.

Dynamic range is the ratio between an audio signal’s highest playable amplitude and the loudest part of the background noise in the sound system.

The SNR is a closely related parameter that indicates the ratio between a signal and the background noise generated by audio hardware or quantization errors.

A higher dynamic range and SNR mean the volume threshold at which one starts to hear quantization and device-related noise bleeding into the recorded signal. These parameters indicate how loud the audio must be played before background noise becomes audible.

Increasing the bit depth decreases the noise floor, resulting in audio recordings with a higher dynamic range.

The dynamic range of 24-bit FLAC is 144dB. By comparison, 16-bit FLAC has a dynamic range of 96db. In practical terms, the human auditory system has a dynamic range of roughly 70dB. So, 16-bit FLAC provides a higher dynamic range (and a lower noise floor) than the human auditory system can perceive.

The increased dynamic range that 24-bit FLAC provides is even further outside the realistic dynamic range of human hearing. This means choosing 24-bit FLAC does not lead to an appreciable improvement in sound quality!

24-Bit Vs 16-Bit FLAC: Additional Considerations

While the difference in the sound quality of 24-bit and 16-bit FLAC is inaudible, some practical distinctions between these bit depths are worth considering. 

Professional Audio Recording And Production

24-bit FLAC is more suitable for professional audio settings than 16-bit.

With 24-bit audio, there is an additional buffer to accommodate the expansive signal range of recording and production equipment. This higher bit depth makes it easier for sound engineers to avoid the introduction of noise and clipping.

The larger amount of information contained in each sample of 24-bit audio enables more accuracy when recreating and processing original audio data.

File Sizes

Capturing more input audio data per sample has advantages in professional studios, but one of the primary disadvantages of high bit-depth audio is the large file sizes. Compared with 16-bit, 24-bit FLAC files are significantly larger.

Consider, for instance, that 24-bit audio potentially holds 16 777 216 bits, while 16-bit audio sampling can only contain a maximum of 65 536 bits.

The increased file size of 24-bit FLAC is inefficient for storing and distributing the audio. In situations where hard drive storage capacity and internet bandwidth are the priority, it is probably advisable to convert 24-bit FLAC to 16-bit.

Laptop screen showing the interface of a music program for working with sound.

Conclusion

The bit depth of FLAC files affects the sampled audio in multiple ways. 24-bit FLAC captures more input data and produces less quantization noise than its 16-bit version. Nonetheless, 24-bit FLAC does not sound noticeably better than 16-bit. Increasing from 16-bit to 24-bit FLAC is generally unnecessary.

The reason for this somewhat counter-intuitive fact is that improvements in the audio sampling of 24-bit FLAC occur at amplitudes and frequencies that are beyond the limits of human hearing. Consequently, the technical difference in the audio quality of 24 and 16-bit FLAC is inaudible to the average person.

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