infrasonic /in-frə-sonˈik/ (acoustics)

1. (of frequencies) below the usual audible limit
2. Of, using or produced by infrasonic vibrations or pressure waves

inˈfrasound noun

• unconcealing
• unconceivable
• unconceivableness
• unconceivably
• unconceived
• unconcern
• unconcerned
• unconcernedly
• unconcernedness
• unconcernednesses
• unconcerning
• unconcernment
• unconcernments
• unconcerns
• unconcerted
• unconciliatory
• unconclusive
• unconcocted
• unconditional
• unconditionality
• unconditionally
• unconditionalness
• unconditioned
• unconditioned stimulus
• unconfederated