96 kHz / 24 Bit Hearing Test DVD

john_dennis wrote on 1/1/2016, 8:48 PM
Some years ago, when I was transferring all my open-reel audio tapes to digital, I used 48 kHz / 24 bit and decided I would deliver them on DVD. The rationale for not using a higher sample rate and bit depth was:

1) 1/4 track, 7-1/2 ips stereo tapes likely don't have any information that warrants anything higher.

2) My hearing doesn't warrant anything higher.

3) Few other people in the world are interested in listening to that crap anyway since they were live stage performances from the 60s and 70s.

As ironic as it may seem, I just bought a music player that reproduces music at 192 kHz / 24 bit uncompressed. I've also downloaded some 96 kHz / 24 bit tracks as well as watched the youtube video of Steven Stills driving all his musician friends around in his old Eldorado playing them tracks on the PONO. All of them bragged about how "real", "transparent" and "live" it all sounds.

Last evening, when I helped a fellow on the forum write some 24/96 PCM to DVD, it made me wonder how these high bit rates and bit depths were serving me.

Today, I decided to make a DVD to test my various equipment and my hearing. (I feel a little guilty for skipping-out on my hearing exam last week for no other reason than I didn't want to be bothered.)

In Sound Forge, I generated sine waves at frequencies from 20Hz to 22kHz. I edited them in Vegas Pro 13 at 96 kHz / 24 bit and prepared accompanying video for DVD Architect.

You may download the DVD folder here and burn it to DVD if you're interested in seeing how your equipment and your ears perform.

[Edit] This is the link to the later version of the project with the audio modulated at 10 Hz.

Disclaimer: This test is not a replacement for a visit to an ear, nose and throat doctor or audiologist.


VidMus wrote on 1/1/2016, 9:49 PM
My left ear can do 4khz at absolute best.

My right ear can do 10khz at absolute best.

My right ear lacks frequencies below 1khz and is approx 20db less than my left ear at frequencies it does hear.

PeterDuke wrote on 1/1/2016, 11:26 PM
Listening to sine waves
In listening to sine waves you are not only testing your ears but your listening equipment and, for loudspeakers, your listening environment.

It is very easy to get reflections (in your ear canal, in the chamber between your headphone and ear, and in your living room), which leads to peaks and troughs in the frequency response.

Audiometers that use sine waves have special headphones that are calibrated at a few discrete frequencies, on test equipment specially designed for the task. Back in my day, the standard headphone was the TDH39 with a prescribed rubber ear pad.

The influence of the sharp peaks and troughs in the frequency response can be reduced by using narrow bands of random noise or warble tones (main tone frequency modulated by say a 10 Hz sine wave) instead of pure sine waves.

Tape recordings
When transferring tape content, don't forget that it would have been recorded with a HF bias, typically set somewhere between 40 and 150 kHz. A low pass filter will then have filtered out most of this, and in so doing, set an upper limit on your recording bandwidth. You really want to get rid of any remaining bias signal or else it may beat with your digital sampling frequency and produce an audible difference tone.

All this is academic to me these days :(
ushere wrote on 1/2/2016, 12:44 AM
all academic to me too ;-(

however, here's my official report:

Hz 250 500 1k 1.5k 2k 3k 4k 6k 8k
L 25 30 30 35 50 70 90 95 95
R 40 35 40 45 55 65 85 85 90

WR left 93%@65db / right 86%@75db

pretty sad eh for a one time soundman...
musicvid10 wrote on 1/2/2016, 8:16 AM
You don't need a hearing frequency test when your favorite response is already, "Huh?"

riredale wrote on 1/2/2016, 12:43 PM
You don't even need 24-bit when coming from tape.

As for frequency limits, I'm at about 12k right now. Back when I was in college many years ago I was easily able to hear 20KHz, but even then it was more of a "sensation" than anything else. Doing an honest A/B test between 16KHz and 20KHz cutoffs with musical material (cymbals, probably) demonstrates that there is very little information at the extreme end of the spectrum.

From the website Head-Fi:
"...So, 24bit does add more 'resolution' compared to 16bit but this added resolution doesn't mean higher quality, it just means we can encode a larger dynamic range. This is the misunderstanding made by many. There are no extra magical properties, nothing which the science does not understand or cannot measure. The only difference between 16bit and 24bit is 48dB of dynamic range (8bits x 6dB = 48dB) and nothing else. This is not a question for interpretation or opinion, it is the provable, undisputed logical mathematics which underpins the very existence of digital audio.

So, can you actually hear any benefits of the larger (48dB) dynamic range offered by 24bit? Unfortunately, no you can't. The entire dynamic range of some types of music is sometimes less than 12dB. The recordings with the largest dynamic range tend to be symphony orchestra recordings but even these virtually never have a dynamic range greater than about 60dB. All of these are well inside the 96dB range of the humble 16bit CD.

So, if you accept the facts, why does 24bit audio even exist, what's the point of it? There are some useful applications for 24bit when recording and mixing music. In fact, when mixing it's pretty much the norm now to use 48bit resolution. The reason it's useful is due to summing artefacts, multiple processing in series and mainly headroom. In other words, 24bit is very useful when recording and mixing but pointless for playback. Remember, even a recording with 60dB dynamic range is only using 10bits of data, the other 6bits on a CD are just noise..."
john_dennis wrote on 1/2/2016, 1:10 PM

My upper limit is around 12 kHz. That's why I included a countdown timer and a red indicator to show that there was some sound being made. I expected other users to respond, "Hey! There's nothing coming out." I also put the .VOB file back on the Vegas timeline to verify that there was, in deed, some sound being made.

Both of them watching the news on TV...

She comments on the story.

He listens attentively.

Then, she asks him what the anchorwoman said while she was talking.

"I don't know."

Disgusted, she walks to the kitchen, turns on the water to fill the sink and reminds him to get his hearing checked.

To which he responds, "Huh?"

DeadRadioStar wrote on 1/2/2016, 6:22 PM
First off, thanks to John for providing the test and raising awareness of the importance of the sense of hearing. Everyone should be aware of what their hearing ability is, if only as an encouragement to be more careful with the sound levels you are prepared to expose these irreplaceable instruments with!

One good thing all hearing tests do is bring a sense of reality into the endless discussions about sample rates. If you know you can't hear anything above 12kHz, there's not much point in wasting money on players that claim to reproduce 192kHz, other than a desire to improve the pension plans of some aging rockers who are probably almost deaf anyway, given their regular exposure to dangerous sound levels in their past careers.

I suspect the most prominent sound in that Eldorado was "ch-ching"!
deusx wrote on 1/3/2016, 12:04 AM
I can still hear 14+ khz sine wave even through laptop speakers. I think around 16.5 khz through nice headphones. I guess not bad for somebody who's owned a Mesa Rectifier stack for 25 years. Then again maybe it just proves I should have played guitar a lot more than I have.
JJKizak wrote on 1/3/2016, 8:20 AM
In my case there is something called "Flush Out" (I invented it) which means when you have the bass turned up it flushes out the highs and when the bass is turned down the highs gain in perceived level. This occurs at higher SPL levels when exceeding the limits of the listening rooms capabilities. If I listen in the adjacent room connected by a doorway it sounds clean. At SPLs around 70-to 75DB everything is clean and the fog level is gone where 80 to 85 starts to get troubling.
It is a struggle to hear anything above 10KHZ with my test tone disc but I can hear the 19HZ tone very well.
john_dennis wrote on 1/3/2016, 12:05 PM

"I guess not bad for somebody who's owned a Mesa Rectifier stack for 25 years."

I suspect the high noise levels of hundreds of computer rooms contributed to my losses. Or the time it takes to visit hundreds of computer rooms.
I'll discount having crash cymbals at ear level. That couldn't hurt.

"I can hear the 19HZ tone very well. JJK"

I could probably hear (feel) 19Hz very well too if I had a driver that reproduced that frequency.

john_dennis wrote on 1/3/2016, 1:45 PM

@ Peter Duke

"Audiometers that use sine waves have special headphones that are calibrated at a few discrete frequencies, on test equipment specially designed for the task. Back in my day, the standard headphone was the TDH39 with a prescribed rubber ear pad."

My headphones are Sony MDR-7506 and they're not calibrated to anything that I'm aware of. I bought them primarily because they have replaceable ear cups. My granddaughter has managed to split the ear cup on one in spite of them being relatively new.

"The influence of the sharp peaks and troughs in the frequency response can be reduced by using narrow bands of random noise or warble tones (main tone frequency modulated by say a 10 Hz sine wave) instead of pure sine waves."

I mixed the different sine wave frequencies with a 10 Hz sine wav and created new project. It can be downloaded from here.

GeeBax wrote on 1/3/2016, 4:43 PM
My hearing is stuffed, my wife talks to me all the time and I don't hear much of what she says. To me it is a blessing....

My hearing loss was caused by years of listening to refrigerator sized JBL enclosures driven by humongous Crown amps in recording studios with rock bands of the 70s and 80s. All mixed together with an atmosphere of weed and cigarette smoke.

Blessed are those who can be selectively deaf...
PeterDuke wrote on 1/3/2016, 5:35 PM
I don't need any smart test to prove what my hearing is like. When listening to television, I sometimes have to cup my ears with my hands to understand what is being said. This lifts the sound in the 1-3 kHz region to compensate for my high frequency loss. (Think of a mountain top at say 100 - 1000 Hz and a ski slope thereafter!)

I can't blame any acoustical abuse for my misfortune - just a card I was dealt.

When TV first came out, the 15,625 Hz tone from the horizontal line generator used to annoy me, but only a few years later I couldn't hear it anymore.

Since we had an audiometer at work, I could track my progressive high frequency loss over the years. My boss, who was 10 years my senior used to brag how much better his hearing was than mine.

I do have hearing aids, but they don't help much, especially if there is noise in the background. It sounds to me as if the lift they give has serious peaks and troughs in the frequency response.
musicvid10 wrote on 1/3/2016, 6:38 PM
Would you recheck your audio render properties?
I got some wierd results.
john_dennis wrote on 1/3/2016, 8:43 PM
I got the same indication in Mediainfo when I looked at the VOB file.

I demuxed the video and audio in tsMuxer and Mediainfo reports the following for the .WAV file from the VOB.

Complete name : C:\Users\John\Desktop\DVD Audio\VTS_01_1.track_160.wav
Format : Wave
File size : 103 MiB
Duration : 3mn 7s
Overall bit rate mode : Constant
Overall bit rate : 4 608 Kbps

Format : PCM
Format settings, Endianness : Little
Format settings, Sign : Signed
Codec ID : 00001000-0000-0100-8000-00AA00389B71
Duration : 3mn 7s
Bit rate mode : Constant
Bit rate : 4 608 Kbps
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 96.0 KHz
Bit depth : 24 bits
Stream size : 103 MiB (100%)

Vegas Reports.

I think it is a Mediainfo reporting error. I have a suspicion that DVD-Video doesn't have 24/96 PCM audio very often (ever). All my optical media drives are Blu-ray and they report real-tine 96 kHz / 24 bit. I'm interested in what people with $30 DVD players see or hear.
DeadRadioStar wrote on 1/6/2016, 4:30 AM
Just reading some of the nonsense about the rash of new "HD" vinyl turntables at CES prompts me to bring this to people's attention:
24/192 Music Downloads
Summary: 16-bit/44.1kHz is good enough for anything (as is 48kHz for the convenience of video heads).
DavidMcKnight wrote on 1/6/2016, 10:24 AM
Really cool John, I plan on taking these tests soon.

@ John Dennis: "I'll discount having crash cymbals at ear level. That couldn't hurt."

Our drummer sat on a riser, so I had snare drum cracks at ear level. 3-4 nights a week for 5 years. That's where I put the blame...
john_dennis wrote on 1/6/2016, 11:34 AM

Thank you for the link DRStar. I found it to be sensible and well written with references. I like to read papers that expose my own sloppy thinking.

@ David

"3-4 nights a week for 5 years. That's where I put the blame..."

It's always the drummers fault.

riredale wrote on 1/6/2016, 12:38 PM
DeadRadio: Well, thanks a lot. I just spent a couple of hours reading your link and other links coming from it. I can't help it, I am fascinated by this stuff, and that's two hours lost forever.

One of the things I re-learned was that the CD sample rate of 44.1KHz was chosen because back in the day of CD development the best way of storing digital audio data was not by hard disk (not enough capacity) but rather by VTR. The audio samples were converted into a video signal by a PCM adapter. Researchers found they could get 6 16-bit samples reliably on each active video line (3 samples for each channel), and working through the math gave a total sample rate of 44.1KHz. Going to a higher sample rate would have made antialiasing filter design simpler, but then other limitations would dominate (going to 7 samples per line would imply a sample rate of 51.45Khz but a less-robust recovery of data from the tape).

There was a strong push for a sample rate of 44.056KHz, which came from using the official NTSC color field rate of 59.94Hz instead of 60. This proposal was rejected, probably because the engineers wanted compatibility with the European 625/25 standard.

Okay, now back to real work (sigh).