A few weeks back, I received an excellent question from a visitor to our site about our tuning forks:
If a tuning fork vibrates at a certain frequency to make a note, and, by definition, every tuning fork that vibrates at the same frequency makes the same note, how can tuning forks sound different if they are the same frequency? You said your tuning forks sound better than others, why would this be?
Well, it really comes down to how the tuning forks are made. Like all things, there are differences in their manufacture, and in the quality of their construction.
There are four main variables that affect the sound of a tuning fork – the length of the tynes (the forks), the cross sectional area of the tynes, and the density of the metal, and a another characteristic of the metal – Young’s modulus which is a measure of the elastic modulus or stiffness of the metal. All are of equal importance.
Coupled with that, are two main processes for making the forks – casting in a mold, or machining from flat stock.
Let’s look at the differences.
Some tuning forks are cast in molds, typically by pouring molten aluminum into a sand mold, Once the metal cools, they are removed from the mold, and the forks are refined – the handles are machined to make them smooth, and the forks are trimmed to length.
Because they are cast, the forks can have inconsistent width and/or thickness on the forks. The geometry of the fork is crucial to the sound. Forks that are not consistent will never have a true tone – the sound will always be contaminated with off-tones – tones that are created by the inconsistencies.
The metals used to cast tuning forks is also much softer, resulting in a shorter playing time. The vibration gives out much sooner. And because the metal is softer, it will deflect easier when striking the fork to activate it. Over time and use, the deflection will take the fork out of tune, and ultimately, make it unplayable.
The only plus that these forks have is price. They are very inexpensive to produce, and so their selling price is also low. This creates a real problem for retailers. When some retailers sell these forks, others have to as well as many people buy on price. It’s hard to sell a fork for $79, when your competitor sells a ‘similar’ fork for $39.
The other way to make forks is to machine them from a solid bar of either aluminum or stainless steel. They are often stamped out in a punch press, and then machined, or the entire fork could be machined.
Regardless of the method, machined forks are known for consistency in the dimensions. This allows for a truer, ‘cleaner’ tone, free of the distortions caused by poor geometry.
The metal bar that is used for machined forks is much harder that that used for forks that are cast. This allows the forks to play much longer than the cast forks, and they are much less susceptible to bending under use.
Of course, these forks also have a disadvantage over the cast forks – they cost more. Machined forks made from aluminum typically cost 2 to 3 times as much as the cast forks. And those made from stainless steel can cost of to 10 times that of a cast fork.
It really comes down to Accuracy
In addition to the materials used to make the forks, and the way that they are made, is the accuracy to which they are manufactured. Accuracy is a huge issue when using forks in sets, such as the perfect 5th forks. Less of an issue when used alone. I have tested forks that are inaccurate by as much a 5% – that’s huge!. A sample fork that I tested that was made as a ‘C’ fork (256 Hz) actually sounded at a B-flat. When used in sets, such as a perfect 5th set, instead sounding harmonious (consonant) they will sound very dissonant with distinct “beating” or wavering when played – a way-wah-wah sound. And it then does the exact opposite of its intent. Good quality forks are generally made with a tolerance of ±0.25%. The majority of manufacturers from the Pacific Rim will only guarantee accuracy to ± 0.5%, and some are much higher.
Our forks are made with a high grade aluminum designed specifically for tuning forks to ensure good tone and a lasting sound. We believe that using a high grade aluminum bar stock gives the best price to quality benefit. Steel bars do make for better tuning forks than aluminum, but we cannot justify the additional cost against the performance improvements. Our forks are manufactured to a tolerance of ±0.2% so the sound is always good, even when played in sets. And we test samples from every shipment of forks that we receive to ensure they are within our specification.