RandomEar
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This post is intended as a reference for when the same question comes up the 1000ᵗʰ time and you don’t feel like typing out why the answer is “NO” again.
Nope. Human hearing is vastly inferior to modern measurement instruments – in most dimensions by multiple orders of magnitude. It’s not even close. We can measure everything we can hear and much more than that on top.
This whole idea of ears somehow being superior is a non-starter, because the majority of the music we listen to and all the music audiophiles describe as “challenging” like classic music, jazz or female singers, has been captured using microphones and standard commercial analog-to-digital converters (ADCs) - which are measurement instruments. So the whole discussion could simply end here, because there is no counter-argument to this: If you think you can hear things which can’t be measured, then how the f*ck could those things ever be part of the recorded audio signal, which was generated by measuring it in the first place? As you can see, the rest of this post is technically redundant because the initial proposition has been debunked.
Let’s nonetheless look at how much better instruments are than ears, just to get a grasp of the amount of hubris which was required to come up with that idea. The following are some important quantities you could measure in an audio signal:
Let’s also discuss some typical counterarguments that come up when talking about measurements:
In a similar manner, old school tube amps often add copious amounts of distortion to the signal, which some listeners describe as pleasing up to a certain degree. We can precisely measure the distortion, but we might not be able to predict today what exact amount is perceived as pleasing and at what point it becomes annoying again. But we can say when it would be audible or inaudible. So for subjective qualities where we can pinpoint specific measured quantities as their source or threshold, we absolutely can predict how and if those will be perceived by humans.
The fact that we don’t know all links between subjective impressions and objective data yet also does not mean that two devices which measure identical in every way might still sound different under otherwise identical boundary conditions: They wont. There’s no “more identical” past “identical”. The only reasonable caveat here is the question if we measured all relevant quantities for a specific device to declare it “identical” to another one. The required measurements for this judgment depend on the type of device (DAC, amp, speaker, etc.) and the boundary conditions under which it is expected to perform. One number alone certainly won't cut it, but nobody around here argues that it will.
Note: If you happen to have better sources for some of the above bullet points, feel free to share them below. If I made a mistake, please let us know how and where.
Nope. Human hearing is vastly inferior to modern measurement instruments – in most dimensions by multiple orders of magnitude. It’s not even close. We can measure everything we can hear and much more than that on top.
This whole idea of ears somehow being superior is a non-starter, because the majority of the music we listen to and all the music audiophiles describe as “challenging” like classic music, jazz or female singers, has been captured using microphones and standard commercial analog-to-digital converters (ADCs) - which are measurement instruments. So the whole discussion could simply end here, because there is no counter-argument to this: If you think you can hear things which can’t be measured, then how the f*ck could those things ever be part of the recorded audio signal, which was generated by measuring it in the first place? As you can see, the rest of this post is technically redundant because the initial proposition has been debunked.
Let’s nonetheless look at how much better instruments are than ears, just to get a grasp of the amount of hubris which was required to come up with that idea. The following are some important quantities you could measure in an audio signal:
- Level thresholds
Humans hearing is limited to a range of about 0 dB SPL at 1 kHz (threshold of hearing) to 130±10 dB SPL (pain threshold) [1, 2]. Even consumer-grade instruments like a MiniDSP UMIK 2 reach about -30 dB SPL @ 1 kHZ in self-noise [3, 4]. Their upper limit is usually around 120-140 dB SPL, depending on the microphone type [5]. Technically, capturing even higher SPLs would be possible, but there are very few use cases where this would be required, which is probably why it’s uncommon for mics to support it.
- Level differences
Humans are actually pretty decent at hearing level differences as small as 0.25 dB for pure tones, with some people in some tests being sensitive down to about 0.1 dB [6, 7] (you can test it yourself here). However, there are multiple effects at play limiting that ideal case threshold during normal listening, like the hysteresis effect [8]. Measurement instruments are more precise than human hearing for level differences, with good analyzers reaching 0.03 dB [9]. But in practice, when measuring with microphones and outside of soundproof chambers, environmental factors like fluctuations in the room noise limit the achievable precision for humans and instruments alike.
If you need to measure precise level differences on speakers or headphones, it is therefore essential to measure the driving voltage using a multimeter instead of measuring the SPL using a microphone or SPL meter. Even cheap multimeters measure down to 1 mV, giving you a much higher precision than any microphone (and also surpassing humans by a good margin).
- Noise
Since instruments can detect sounds at much lower levels than humans, the same is true for noise. As noise can usually be analyzed over longer time scales, whereas instantaneous values may be required for level differences, instruments can gain further sensitivity in detecting noise by increasing the analyzed time frame. Consequently, modern audio analyzers can detect noise at absurdly low levels (< -120 dBFS) [10, 11]. In an odd twist of fate, modern DACs have reached noise levels which are at or below those of the best currently available audio analyzers – but not better than the best lab-grade instruments like precision voltmeters.
- Distortion
Humans can hear distortion in real music down to about -40 dBFS (= 1%) with instant A/B switching [12]. For speakers, it is generally assumed that distortion below 0.3% or -50 dBFS won’t be audible [13]. However, with pure tones in very favorable (artificial) scenarios, some people can reach a threshold of close to -80 dBFS with very high order harmonics (>20th order) [14]. Even better consumer-grade ADCs like the E1DA Cosmos can easily detect distortion down at -140 dBFS, though, which is just insanely far away from anything any human could ever even dream of perceiving [15].
The reason the threshold numbers for humans diverge so much is that THD and IMD are not well correlated to the audibility of distortion: Distortion components close to the original tone can be fully masked even at very high levels, while higher order distortion can be easier to detect due to the lack of masking [11, 16]. Nonetheless, absolute lower thresholds have been established for THD and IMD and are valid. Multiple psycho-acoustic models exist which correlate significantly better with the audibility of distortion [17]. But in practice, manufacturers and reviewers alike publish THD or IMD numbers: They are easy to measure with great precision and are the de facto industry standard.
- Frequency thresholds
Human hearing is usually accepted to be limited to a range of 20 Hz – 20 kHz for young listeners and the upper hearing threshold quickly degrades with age [18, 19]. But even if you assume that we might hear slightly above or below those limits, instruments can measure anything from 0 Hz to multiple 100 kHz for audio analyzers and into the MHz and even GHz range for oscilloscopes and spectrum analyzers [20, 21]. So, no chance for humans to compete.
- Frequency differences
Modern audio analyzers are precise to 10⁻⁵ Hz or better, whereas humans usually fail to detect differences below 1.0 Hz in test tones [10, 22]. There’s just no contest here.
- Time precision (“Timing”)
For better consumer ADCs capturing signals at 192 kHz and 24 bit, the intersample time is 5.2 µs. However, the actual time resolution is significantly higher due to the sampling theorem and clears the nanosecond range [23, 24]. In addition, different measurement instruments like consumer-grade oscilloscopes can easily display a fully resolved 50 MHz sine wave, which takes 20 ns for one full oscillation. This means the time resolution of the scope must be significantly better than that. For humans, the agreed upon number is somewhere between 7 and 18 µs, which is multiple orders of magnitude worse than instruments [25, 26].
- Phase differences
As phase differences are effectively time differences for specific frequencies, the same arguments concerning timing (and frequency) precision made above hold and human ears are far outclassed by measurement instruments.
Let’s also discuss some typical counterarguments that come up when talking about measurements:
- “But I can hear differences, even though the measurements say there are none!”
There’s three options:- Your specific device(s) are defective and there actually are differences where there would be none in an undamaged device.
- You did not account for all boundary conditions and tested incorrectly. For example you may have missed to level-match to within 0.2 dB (ideally 0.1 dB) or you are using audibly different filters, EQ or other settings. Your seating position may have changed, or you may have taken more than a couple of seconds to switch between the settings or devices you tried to compare.
- You are mistaken and are a victim of bias, like any other human could be. Or in other words: Your brain is tricking you and the differences would instantly vanish in controlled (double) blind testing. This is by far the most common and prevalent error in audio testing when done by a layperson.
- “But there’s more to an audio signal than time and voltage/current!”
No, there absolutely isn’t. You can watch everything which makes up the analog audio signal on a two-dimensional oscilloscope screen. There’s time, there’s amplitude, that’s it. As amplitude, you can either measure voltage or current. The current is a direct result of the voltage being present: If two audio signals have an identical voltage curve on a specific system, their current curve will also be identical.
- “Science hasn’t fully understood it, yet!” / “We discover new things all the time!”
If that were true and even assuming that the science behind some basic electronics somehow were incorrect, you would still easily be able to prove that such a problem exists using well controlled double blind listening tests. As long as no such evidence exists, that whole assumption is flawed: You can’t postulate major errors in some of the most well understood fields of engineering without providing any evidence and expect people to take you seriously.
The reality is that in relation to electric and acoustic signals (like analog and digital audio), science has understood these very well for over half a century. We – for the most part – also know what we don’t know. We have applied knowledge from all the fields of science and engineering related to these topic to build devices like acoustic metamaterials or phased array antennas. If there were any fundamental errors in the basic science behind it, these things would simply not work.
The fact that an individual might not understand all the theories and calculations used to design a specific device does not invalidate the science behind it. On the contrary, if an opinion is uninformed, the opinion itself should be the first thing to be questioned.
In a similar manner, old school tube amps often add copious amounts of distortion to the signal, which some listeners describe as pleasing up to a certain degree. We can precisely measure the distortion, but we might not be able to predict today what exact amount is perceived as pleasing and at what point it becomes annoying again. But we can say when it would be audible or inaudible. So for subjective qualities where we can pinpoint specific measured quantities as their source or threshold, we absolutely can predict how and if those will be perceived by humans.
The fact that we don’t know all links between subjective impressions and objective data yet also does not mean that two devices which measure identical in every way might still sound different under otherwise identical boundary conditions: They wont. There’s no “more identical” past “identical”. The only reasonable caveat here is the question if we measured all relevant quantities for a specific device to declare it “identical” to another one. The required measurements for this judgment depend on the type of device (DAC, amp, speaker, etc.) and the boundary conditions under which it is expected to perform. One number alone certainly won't cut it, but nobody around here argues that it will.
Note: If you happen to have better sources for some of the above bullet points, feel free to share them below. If I made a mistake, please let us know how and where.
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