It hurts to say "Hertz".
D004866:Equipment Contamination; D006612:High-Frequency Ventilation / Q000009:adverse effects* / Q000379:methods; D006801:Humans; D016272:Occupational Health; D012138:Respiratory Therapy / Q000009:adverse effects* / Q000379:methods / Q000523:psychology; D018570:Risk Assessment; D014777:Virus Diseases