Tuning fork quality

Tuning fork quality

The Sound Therapy Shop sells top-quality aluminium tuning forks manufactured in America and India.
We have carried out our own tests to compare 2 types of tuning forks from different manufacturers:

Accuracy

A Biosonics tuning fork is guaranteed an accuracy of +/-0.5. This allows for temperature changes and testing variations.
An Indian tuning fork is guaranteed an accuracy of +/-0.25%.
We have found that both types of tuning forks normally fall within the accuracy range of +/-0.25%.

Testing results

The Mid-Om forks were tested at exactly 136 Hz, which is accurate to 0.07%.
Unweighted C tuning forks (256 Hz) - Biosonics tested as 256 Hz (spot-on) and the Indian fork to 256.5 Hz, so the accuracy was 0.18%. This is within the guaranteed range. 

Spectrogram Comparison: Mid-Om Weighted Tuning Forks

The forks were tapped using the same mallet at similar velocities and held in a similar position close to the microphone of an iPhone 12 Pro, one minute apart, thereby maintaining similar environmental conditions.

Harmonics

The 2 images below provide a comparison of the harmonics of the 2 types of tuning forks. The harmonics are shown by the thin white lines in each image.
136.1 Hz Mid-Om Weighted American (Biosonics) Tuning Fork
OM weighted Biosonic tuning fork
136.1 Hz Mid-Om Weighted Indian Tuning Fork
OM weighted tuning fork India

Comparison of harmonics & sustain

Both brands of tuning forks display the same 10 frequencies and the sustained pattern for each harmonic is similar.

Conclusion

For this type of tuning fork, the spectrogram comparison shows that there is little difference between the two brands of tuning forks. 

Spectrogram Comparison: 256 Hz Unweighted Tuning Forks

The tuning forks were tapped using the same mallet at similar velocities and held in a similar position close to the microphone of an iPhone 12 Pro, one minute apart, thereby maintaining similar environmental conditions.

Harmonics

The 2 images below provide a comparison of the harmonics of the 2 types of tuning forks. The harmonics are shown by the thin white lines in each image.
256 Hz Unweighted American (Biosonics) Tuning Fork
256 Hz unweighted biosonic tuning fork
256 Hz Unweighted Indian Tuning Fork
256 Hz unweighted Indian tuning fork

Results 

The Indian tuning fork displays more harmonics - 9 harmonics with the Indian tuning fork compared to 7 harmonics with the Biosonic tuning fork.
3 of the higher harmonics of the Biosonics tuning fork are shown to be more audible with greater amplitude and to have a longer sustain than the Indian tuning fork.

Sustain

Audible sound

We tested how long each fork could be heard after activation. Mid-Om forks:- Biosonics 48 seconds and Indian 39 seconds Unweighted C fork:- Biosoncis 42 seconds and Indian 32 seconds.

Felt vibration

We tested how long the vibration of each Mid-Om tuning fork could be felt after activation. Each fork was activated and placed on Jane's sternum and timed to discover at what point the vibration died away.
The felt vibration of the Biosonic tuning fork lasted 18 seconds, while the Indian tuning fork lasted 14 seconds.
The 2 images below provide a comparison of the length of sustain of the 2 types of unweighted tuning forks using a spectrogram analysis - see the lowest thin white line.
256 Hz Unweighted American (Biosonics) Tuning Fork
256 Hz unweighted biosonic tuning fork 
The fundamental tone of the Biosonics fork (256 Hz) has an audible sustain that lasts about 42 seconds.
256 Hz Unweighted Indian Tuning Fork
256 Hz unweighted Indian tuning fork
The fundamental tone of the Indian fork (256 Hz) has an audible sustain that lasts about 32 seconds.

Overall Conclusions

Both makes of tuning forks had a high level of accuracy.
The harmonics are similar in both makes. There are slightly more harmonics in the Indian tuning fork. However, the American tuning forks display a slightly higher amplitude (louder sound) of audible harmonics.
The main difference we found is in the sustain, which is longer in the Biosonics tuning forks. This is in both audible sound (approximately 10 seconds longer) and felt vibration (4 seconds longer).
The Indian tuning forks perform very well compared to Biosonics. We have been using Indian forks successfully for ten years and they are great value. At our shop, we have a wide range of tuning forks available.
Biosonics tuning forks are a premium product and they do have the edge in terms of sustained note and a higher amplitude of audible harmonics.