in·fra·son·ic 
(ĭn′frə-sŏnĭk)
(ĭn′frə-sŏnĭk)adj.
Generating or using waves or vibrations with frequencies below that of audible sound.
- electrocardiographic
- electrocardiographically
- electrocardiography
- electrocautery
- electrochemical
- electrochemical cell
- electrochemically
- electrochemist
- electrochemistry
- electrochromic
- electrocoagulation
- electroconvulsive therapy
- electrocute
- electrocution
- electrode
- electrodeposit
- electrodeposition
- electrodermal
- electrodialysis
- electrodynamometer
- electroencephalogram
- electroencephalograph
- electroencephalographic
- electroencephalography
- electroform