Tuning Forks
Iconographie photographique de la Salpêtrière vol. 2
"If you want to find the secrets of the universe, think in terms of energy, frequency, and vibration"
Nikola Tesla (1856 –1943), Serbian-American engineer
History
1550 Gerolamo Cardano - transmission of sound per skull
1684 Schelhammer - fork to differentiate hearing disorders
1711 John Shore - invented TF
1834 Johann Heinrich Scheibler - different frequencies
1855 - Weber test
1870 - technical improvements
Parts
Prongs (wings), stem (handle), and foot (base)
Motion
- air pressure changes out (compression) & in (rarefaction)
- pure tone (1-dominant frequency) 2/2 simple shape
- fixed frequency (wings length, thickness, material)
> striking hard change amplitude, but not pitch
Classification
- based in frequency: 128, 256, 512, 1024 and higher (research)
> ⬇️ Hz for vibration; ⬆️ Hz for acoustic
> more specific: 128 for vibration and 512 for acoustic
- weighted vs non-weighted
> "Weight feel; no weight hear"
> weight effects: ↓vibration frequency stability; ↑amplitude & duration of vibration; ↑tactile (vibratory) sensation; ↓sound clarity
- quantitative vs non-quantitative
> quantitatives: Rydel‑Seiffer
*vibrameter/biothesiometer - electronic vibration device
Use
- over bone surfaces
- neurological (assess post column) and otological (assess hearing)
- air (indirect) versus bone (direct) conduction
Tests
- Rinne: air vs bone conduction
- Weber: lateralization of sounds
- Schwabach test
> examiner normal hearing
1st place TF on patient's mastoid
2nd patient tells no longer hearing tone
3rd examiner place TF on his own mastoid
- Bing test
> TF placed on mastoid, finger used to alternately open&close ear canal
- ABC (absolute bone conduction)
> Schwabach test with tragus closed, to avoid ambient sound
- Gelle test
> TF placed on mastoid, Siegel speculum for air pressure on TM
Summary
Rydel‑Seiffer
Interesting
- most common clinical TFs are C and its octaves (C3 512Hz; C1 128Hz); in music, standard is A (A4 440Hz)
- A440 (pitch standard, Stuttgart pitch)
- TF, sinusoidal curve, 2 TFs and Lissajous figures
