Which type of communication can be utilized in noisy environments where voice is ineffective?

Using whistles for communication in noisy environments is highly effective due to their ability to produce a loud, piercing sound that carries over background noise. This makes whistles a reliable tool for signaling and getting attention, especially in situations where voices may not be heard, such as during water rescues or when dealing with large crowds or machinery noise. Unlike verbal communication, which can become muffled or lost, a whistle's distinct sound can easily cut through ambient noise, allowing rescuers to communicate critical information rapidly and clearly.

Additionally, while hand signals and facial expressions can be useful, they rely on visibility and the ability of the other person to see the signals accurately amidst noise, which can be challenging. Cell phones, while useful, depend on reception and the ability to hear clearly, making them less practical in particularly loud environments when immediate and clear communication is necessary.