I have a tuning fork and a tuning app on my tablet. I am interested to know which to trust.

The tuning fork is old. It was my father's (for his violin) and hence is probably from the 1930s at the latest (maybe older if it was second hand or from his father).

The tablet is a Samsung Galaxy Tab 5 and runs Android. The app is called DaTuner Lite.

The app says that the tuning fork is 438.2Hz. So, I am wondering which is more likely to be right. Is the tuning fork slightly flat or the app underreading slightly?

An alternative phrasing of the question is how accurate are these cheap or free apps?

Obviously, this small error is not important, I am just curious.

Extra detail.

On one side it says: "British Standard A".
On the other it says: "England John Walker".

There's no indication of the frequency that it claims to be.

Another test.

I just realised that I can perform another test. Some years ago, I wrote a Java program which generated a series of WAV files containing pure sine waves at various frequencies. These include A4 at 440Hz. I just played that and the tablet reported it as 440.2Hz. So, closer than the tuning fork. I think that I can now conclude that the tuning fork is probably not 440Hz, maybe it is intended to be 438Hz as mentioned by Bob. The .2Hz difference is interesting. I need to review my code. It seems that either I, or the author of the app, has a rounding error. If we assume that the tuning fork is exactly 438Hz then it is curious that the app overreads it and my test tone by the same .2Hz.

And another test.

I found a recording of an orchestra tuning up. It was the Liceu Barcelona. It was hard to get a clear reading from the app as there was lots of other noise but at one point, it seemed to catch the oboe; it read 443Hz (with some fluctuation of about .2 or .3 above). So, another confusing data point.

And even more data.

I installed another tuning app on the same tablet. It reports my test tone as 440.3Hz. So, even if my test source is wrong, it suggests some level of error in these apps as one consistently reports 440.2Hz and the other 440.3Hz. Of course, the true value may be close to midway between the two. I also installed the first app on a different device, Samsung again but a phone rather than a tablet, it also reported 440.2Hz.

  • 1
    Is it a 440Hz fork? There are plenty of 438Hz forks out there. – Bob Mar 3 '18 at 15:56
  • @Bob - were they from an era when A =438Hz? – Tim Mar 3 '18 at 16:02
  • @Bob It didn't occur to me that it might be deliberately not 440Hz. However, it does not say, see the extra detail that I just added. – badjohn Mar 3 '18 at 16:03
  • A search for 438Hz got a few hits but nothing very definitive. However, if that era covered the early 1900s then it would explain it. Searching for "British Standard A" was not very effective - masses of irrelevant hits. – badjohn Mar 3 '18 at 16:07
  • 2
    If it says British Standard then it's probably referring to 440Hz, but that wasn't agreed as a standard until 1939. – Bob Mar 3 '18 at 17:33

Well, to answer your question directly: Computers are rarely that off. The difference between 440 and 438.2 is about 0.4%. Now, the tuner app does two things: (1) records the input and (2) analyses it.

As for (1), if the inner clock were off by 0.4%, the tablet would be off by 6 minutes a day, very unlikely. As for (2), this is also very unlikely as the frequency analysis of well-formed tones such as fork tuner tones is easy and should be precise, unless the app is very poorly made.

Conclusion: It is safe to assume that the tuner is 438.2Hz, and not 440Hz.

  • Thanks. I expected that but hoped for some confirmation. Indeed the tablet's timing is unlikely to be far off. I was less sure of the likely quality of the programming in cheap and free apps. Oddly, it had trouble noticing the tuning fork and I had to experiment with the position and orientation for some time. It notices notes from the piano and voice reliably. – badjohn Mar 3 '18 at 18:28
  • Have you tried putting the base of the fork directly on the tablets rim? (Similarly as if you put it on a hardwood table to make it louder.) – yo' Mar 3 '18 at 18:39
  • Yes but oddly that is less effective than putting it on the piano and the tablet near to that. – badjohn Mar 3 '18 at 19:04
  • Is the accuracy of the app only likely to be limited by the clock? Don't we have to know exactly how the analysis algorithm works before we assume that? – topo morto Mar 4 '18 at 9:00
  • 1
    @topomorto Well, you can try other algorithms/apps, or you can try a 440Hz wave generator on another device and do a test. – yo' Mar 4 '18 at 15:56

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