Which types of military helicopters do not have noise attenuation within the damage risk criteria when helmets are worn properly?

The correct choice, which consists of the UH60 and CH47 helicopters, accurately reflects specific operational characteristics regarding noise exposure and the effectiveness of protective gear like helmets.

Research indicates that these particular helicopters operate in environments where the noise levels can exceed safe thresholds, even when personnel are wearing properly fitted helmets. This means that despite the use of helmets designed for noise attenuation, the sound frequencies produced by the rotor system and engine of these helicopters can still pose a risk, particularly during prolonged exposure.

The UH60 is known for its diverse operational roles, and the CH47 is recognized for its heavy-lift capabilities. Unfortunately, due to the nature of their rotor systems and engine noise, they generate sound profiles that can surpass damage risk criteria, emphasizing the need for ongoing monitoring and protective measures.

Considering the other helicopter combinations provided, they either feature helicopter types that are better equipped to manage noise, or there are discrepancies in the operational data relating to noise risk criteria. For instance, the AH64 and CH53 helicopters, while still capable of producing significant noise, demonstrate different levels of sound exposure management compared to the selected combination.