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Anyone have a suggestion for a good simple small electronic pure sine wave A-400 source? Something that I can be certain does not output noticeable harmonics other than the fundamental. Frequency adjustment around 440 for those occasions when someone wants a non-standard tuning would be nice, but not critical. Not currently using an EDT, so that suggestion doesn't work here. I've tried tuning forks, but I find that a steady hands-free source works much better for me.
Thank you,

I made 7 of them for the PTG Foundation auction at the 2008 convention. I had considered making them a real product, but the demand was not high enough to justify it. Bill Bremmer has sampled them. If I see enough interest, I may reconsider.

Robert Scott
TuneLab

@Jerry Viviano

I think this is very close to your description: http://www.accu-tuner.com/AF.html


@Robert Scott

Do you have any pictures? Do you have an estimated price figure?

I can give you several prices. The ones I hand-made, in custom finger-jointed and hand-stained oak boxes, would cost about $150 each. If they were made in slightly larger quantities with a molded plastic box, they could sell for $60 each. And if they were made in very large quantities using mass-production techniques, they could sell for $10 each. It's all about the quantities. If anyone would like to take over production, I would be willing to part with the electronic design for a very small fee. Send me a PM if you are interested.

By the way, the Accu-Fork cited earlier has very strong 3rd and 5th harmonics. Bill Bremmer can tell you call about the problems that causes examinees in the tuning test.

Robert Scott
TuneLab

Yes, I agree that the Accu-Tuner would be likely to have numerous harmonics. Its web page says "It still has same size and weight and the same pleasant overtone-rich oboe-like tone quality."

Don't want overtone-rich. I'm looking for something with no overtones. Given the likely customer base for this product and the history of the Accu-Tuner product line and company, it's surprising that they would put out something with strong harmonics. Could be a case of "If you can't fix it, feature it."

Yikes, thanks for the information. I was not aware of those strong partials.

A better alternative for $60 or less sounds good.

That sounds really, interesting! Do you have any pictures of it, Bob? Maybe we could get a list of folks who would be interested in going in on a bulk order. I love the idea of it being made out of wood!

Though if you've studied Jim Coleman's 12/2008 Journal article on setting pitch, you should be able to make use of that 3rd partial with practice. The basic technique is to tune the 3rd partial of A4 against the corresponding 3rd partial of the device, and set it for 3-4 bps sharp. Not a "purist" technique, but can be accurate, easy, and fast.

I carry a relatively cheap Seiko SQ-50 (about $30 a few years ago) as a backup for Tunelab, but the technique should work for the slightly off-pitch sources with 3rd partials as well.

(But I still carry an actual, physical, backup fork in case all else fails :D)

OK, here's a picture. For reference, the finger joints are 1/4 inch. The device can generate 400.0 Hz to 999.9 Hz in steps of 0.1 Hz with quartz accuracy. It also functions as a beat-rate generator for aural beat rate training, generating 0.1 to 19.9 beats per second in steps of 0.1 beats per second.

Jerry, you can have the one Robert made for me to try out. It is better than any device which has a strong second partial but with no inharmonicity. That is where the problem with any of the devices lies, as I have discussed with you. Robert has made the one and only device with no second partial that I know of.

The problem for Robert is that to make the devices, he would be selling to an extremely small, niche market, namely only those who want to take the PTG tuning exam! Otherwise, any other device that is reasonably accurate is OK.

The PTG tuning exam has a tolerance of 1.0 cents. Anything within that scores a perfect 100. For every 0.1 cents either sharp or flat of that, there is one point off. The problem with the zero inharmonicity second partial of virtually any other device is that it can easily cause the tuner to tune A4 flat by the amount of inharmonicity between the first and second partial of A4 on the piano. That is usually at least 1 cent. When I used such a device for a master tuning with two other examiners of the highest caliber and years of experience, we encountered that problem. Among all three of us, our aural perception told us that we needed to flatten the pitch of A4 when we could see that A4 measured perfectly electronically. We had to switch to a tuning fork to make aural verification of A4 work for us.

At the time, we did not understand why but we figured it out later. I talked to Robert about the problem and he came up with a solution but he did not find enough interest in the product to make it worth while. Therefore, I continue to recommend the use of a properly calibrated tuning fork. However, Jerry, because you have been so helpful to me, I would gladly give you the device Robert made for me to try out.

Maybe a resonance box will do it. Drill a hole on it and you can switch tuning forks.

Jerry, a hands free solution for the fork would be to wrap the handle with a bit of masking tape and after striking, hold between your teeth. The bones in your head will transmit and amplify the sound to your ear. I used this method for years.

I wonder if those small digital voice recorders could be utilized to record the sound of a pure 440 hZ sine wave tone generated through a computer off one of the many frequency generator programs out there. You would have to calibrate first but I'm sure the reproduction of the sound would be accurate.

I too, use the fork to teeth method. But masking tape is not enough to keep the vibrations from loosening any fillings you may have in your teeth. You gotta be careful...very careful.
I've tried looping a small rubber band around the tip of the fork, but the best thing is a small piece of plastic tubing that you can buy at about any hardware store. No matter what you use, if you do this, it is best not to leave the fork vibrating between the teeth for long.

Yes, I still have most of my teeth!!!!

I hold my tuning fork against the bone just below my ear, opting for volume rather than having both hands free.

Bill,
That's quite an offer. I will likely take you up on it if I can't find another solution. May have to send you another jar of spaghetti sauce. I will continue working on finding a successful approach to using a simple tuning fork. If I can't find one, I will ask to borrow your Robert Scott tone generator. That's quite a piece of handiwork. I did dovetailing once when I built all of the drawers for our kitchen cabinetry. I know that it can be challenging, but it looks like he did a good job.

On a side note, almost certainly the objectionable harmonic which you hear from the electronic tone generator is not the second, but the third harmonic. It is very easy for electronic devices to create what is referred to as a square wave. Fairly difficult for them to create sine waves without harmonics. Pure square waves contain only odd harmonics. 1st, 3rd, 5th, 7th, and so on. The relative power of these harmonics would be 1, 1/9, 1/25, 1/49, and so on. It is possible though for a cheap loudspeaker or other lousy audio transducer to inject even harmonics into a square wave. Being familiar with these signals from my engineering and math background is why I'm avoiding them, and asking if there is a small electronic device that only produces the fundamental.

On the topic of the tuning fork in the teeth. Yes, I had tried this many times with the handle covered with a piece of plastic tubing. Nice loud tone, with good sustain. However, there is something quite annoying that comes with this which I completely don't understand. Instead of a nice steady pure decaying tone, I hear that, but with a very narrow dropout in volume, perhaps less than a tenth of a second. This dropout occurs periodically about once a second and makes using it as a pitch source nearly impossible for me. Me, with my grandiose masters degree in signal process, I have absolutely no explanation for this. If someone does, please let me know. Has anyone else ever observed this?

Thank you,

Jerry, I like Emmery's idea. It is worth a try. You can use any audible device so long as it has no visual cues or display.

Right,
I like Emmery's idea as well. I will have to dig out the digital voice recorder buried in the bedroom closet somewhere.

In the past hour though, I have built a small 440 Hz quarter wavelength resonant cavity out of a piece of PVC tubing. Speed of sound in air is 1125 feet/sec.

1125 feet/sec / 440 / 4 = 0.64 foot = 7.7 inches of PVC

I attached my tuning fork to the open end and shut off the other end with a a block of wood. That actually worked out pretty good. Nice clear hands-free long lasting tone.



But it's kind of big and clunky. Will try the voice recorder.

Thanks,

Nowadays it's pretty easy to design and build a sine wave generator that is accurate and settable. The real problem is finding a market, and building it cheap enough that people will be willing to buy it.

“Speed of sound in air is 1125 feet/sec.”

Not exactly……..

The speed of sound in air is 343 m/s or 1126.547 ft/s (768.095 mph) at a temperature of 20°C or 68°F.

http://www.science-house.org/teacher/empower/SpdSound.html

Actually I always thought that it was 1132 ft. per second at 32 degrees and for every degree is rise this would change by 30 ft. but after reading the link I provided I am not so sure any longer….

Jerry, I am sure the examiners would find your set up interesting. It's always nice to see something unusual that someone has come up with. If neither that or the voice recorder works out, you can always borrow the device from me until you get your exam taken and passed then return it later.