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I am glad you had success, but I don't understand the computer's clock inaccuracy.
Anyway, it was wise to do the calibration, and I wish you success in tuning.
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Just out of interest, did you use a landline phone for the calibration, and, if so, is it Voice Over Internet Protocol?
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Could you me a favour and record a tone from the Tunelab tone generator (440Hz) and send me the file? I would love to check the accuracy. Any recording would do. I just need about 10 seconds of the tone.
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Yes, I did use VOIP for the calibrations and double checks. Do you think that matters?
I could try a cell call to see if there is a difference....
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I just did the calibration using a cell call to NIST. Same result (-11.2 offset)
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VOIP uses clocks on both ends of the transmission. Each layer of conversion adds error to the chain, but it shouldn't be that far out. If you have an analogue radio that can pick up WWV on 2.5, 5.0, or 10MHz, that is the best source for an accurate NIST signal. The small errors in transmission get averaged out over the 3 minute transmission.
Anyway, if you could record the Tunelab tone generator (1000Hz for 10 seconds would be even better than 440Hz) I could anaylize the file and check the accuracy. You can PM me and I'll give you an email address.
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Could you me a favour and record a tone from the Tunelab tone generator (440Hz) and send me the file? I would love to check the accuracy. Any recording would do. I just need about 10 seconds of the tone. How do I attach a file to a reply?
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Unfortunately, the only way I know to attach an audio file to a post is through a URL link to a server where the file is stored. You would have to upload it to the server, then place the link in your post using the 'Use Full Editor' reply box.
It is easier to send me a PM and I will give you my email. Just directly attach the file to the email.
Last edited by prout; 08/18/17 05:55 PM.
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Silly me. I just sent you a PM. look for the flashing red/white at the top near "My Stuff".
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sam1 and I have been working on Tunelab calibration and it seems that we have discovered an anomaly.
When Tunelab is calibrated from a known and accurate source, it appears that Tunelab establishes the computer clock error, and then adds an offset to the microphone sensed pitch and displays the corrected pitch.
However, Tunelab does not appear to add this calibrated offset to the tone generator. This means that any tone produced by Tunelab is in error by the amount of the calibration offset.
For example, sam1 found that Tunelab needed an offset +11.2 cents to display the correct pitch. He made two files, one of the calibrated Tunelab tone generator produced 440Hz sound, and one of the uncalibrated Tunelab, and I measured both files at 437.01Hz, or about 11.8 cents flat.
Does anyone else using Tunelab97 find this anomaly?
Last edited by prout; 08/19/17 09:48 AM.
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sam1 and I have been working on Tunelab calibration and it seems that we have discovered an anomaly.
When Tunelab is calibrated from a known and accurate source, it appears that Tunelab establishes the computer clock error, and then adds an offset to the microphone sensed pitch and displays the corrected pitch.
However, Tunelab does not appear to add this calibrated offset to the tone generator. This means that any tone produced by Tunelab is in error by the amount of the calibration offset.
For example, sam1 found that Tunelab needed an offset +11.2 cents to display the correct pitch. He made two files, one of the calibrated Tunelab tone generator produced 440Hz sound, and one of the uncalibrated Tunelab, and I measured both files at 437.01Hz, or about 11.8 cents flat.
Does anyone else using Tunelab97 find this anomaly? I downloaded the program and checked. Out of the box it generates 440.00000Hz, if I deliberately calibrate to say 443Hz then it generates 443Hz. So the anomaly must be user error. Kees
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Thanks for checking it out. Good to know.
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I have TuneLab Pro 5.0 and it is not calibrated. Out of the box it generated on my laptop, and was recorded by my iPad, by my measurements, 439.9989Hz, which, given the sample size and doppler effects from my shaking hand holding the iPad to the laptop mic, close enough to 440Hz to declare it accurate.
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When I designed TuneLab I assumed that if there were any errors in the sound system crystal frequency they would be the same errors whether generating a tone or listening to a tone (audio output vs. audio input). Usually this is true because one crystal drives both processes. Therefore one calibration would correct both tone generating errors and listening errors. But I found out that some PC sound system hardware (and Pocket PC hardware too!) had calibration errors that were different for output and input. Therefore you could calibrate listening mode perfectly and find that tone generation was in error. Apparently these PC sound system makers for some reason decided to use separate crystals for sampling output vs sampling input. (I have not found any similar discrepancy in Android or iOS devices, so we don't don't make any provisions for this problem in the iOS or Android versions of TuneLab.) Since most people use listening mode exclusively for tuning, it was not a huge problem. But TuneLab Pro does have provisions for calibrating tone generation mode separately from the input mode. So keep this in mind when performing experiments on calibration. One provision is to calibrate for input first, and then use that results of that calibration to determine output calibration internally by running a concurrent input and output process and timing them both. It takes a few minutes. As I said, in most cases the two calibrations will turn out the same. We focus our main attention on calibrating input mode, since that is the mode that most people use for fine tuning. (Tone-generating mode can be useful for chipping a new piano at the factory, but then absolute accuracy is not important.) Previously our input calibration relied on comparisons with an externally supplied pitch, such as the NIST tones or a precise tone generator. We recently added Internet Calibration to TuneLab Pro as an option for people who do not have access to a precise reference tone. Even though calibration to reference tones takes only a few seconds, Internet Calibration takes up to 6 hours because it relies on accurate time-of-day references from Internet time servers. Because of the uncertain delays experienced by Internet packets, it is difficult to get a time-stamp any closer than 0.05 sec. To make this time insignificant we must take two time stamps several hours apart. There is an option within Internet Calibration to cut the 6 hour period short and figure the calibration based on a shorter sample time. I have used this an gotten reasonable calibrations in as little as 20 minutes instead of 6 hours. But it is not guaranteed. I set the limit at 6 hours because that guarantees Calibration to within 0.01 cents even with a marginally slow Internet connection. If you only want accuracy to within 0.1 cents, then you can use 1/10 of the time and complete the Internet Calibration in 36 minutes. But if you are going to tie up your PC to this dedicated process for 36 minutes, you might as well leave it on overnight and be absolutely sure of the accuracy. For those interested in Internet Time Servers and how they are normally used to synchronize time in PCs and other devices, just google "Network Time Protocol", or visit www.ntp.org.By the way, prout, if someone records a tone for you and sends you the audio file, that does not prove anything. The precise sample rate of their audio recording system might not match the precise sample rate of your audio playback system. So you would not necessarily be rendering the audio at exactly the same frequency at which it was produced.
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Robert,
Thanks for chiming in. It is greatly appreciated.
Yes, I understand the inherent limitations of digital file sharing, though, these days the error seems to be in tenths of a cent rather than in cents, based on my own sharing amongst fellow measurers when using a known analogue reference. Edit: I should also say that I measured the sent file using four different DACs and that they agreed to with a few hundredths of a hertz at 437Hz.
I did not know that some computers used separate crystals for input/output sampling. Very interesting. Funny, I should have thought of that. I sometimes use one of my two outboard ADC/DACs for output while using the computer's soundcard for input. This is done out of convenience, not quality.
I think the 6 hour time interval is a brilliant solution to the verious errors that can creep into a time signal. I did the same thing back in the days of 'Selective Availability' GPS by doing a two dimensional plot of a fixed known position. The data over a period of 24 hours would converge on the known location to within a few centimetres from an initial starting positional error of up to 100 metres
Last edited by prout; 08/20/17 11:38 AM. Reason: added info
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I did the same thing back in the days of 'Selective Availability' GPS by doing a two dimensional plot of a fixed known position. The data over a period of 24 hours would converge on the known location to within a few centimetres from an initial starting positional error of up to 100 metres I'm sure the surveyors were happy when President Clinton turned off SA.
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Piano
by Gino2 - 04/17/24 02:34 PM
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Piano
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