Why do hydrogen fuel cells produce little noise during operation?

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Diagram of a proton exchange membrane (PEM) fuel cell showing labeled layers, including flow field plates, electrodes, and the proton exchange membrane, with arrows indicating hydrogen and oxygen inputs, electricity generation, and water and heat as outputs. — fuel cell Proton exchange membrane (PEM) fuel cell
The proton exchange membrane is one of the most advanced fuel cell designs. Hydrogen gas under pressure is forced through a catalyst, typically made of platinum, on the anode (negative) side of the fuel cell. At this catalyst, electrons are stripped from the hydrogen atoms and carried by an external electric circuit to the cathode (positive) side. The positively charged hydrogen ions (protons) then pass through the proton exchange membrane to the catalyst on the cathode side, where they react with oxygen and the electrons from the electric circuit to form water vapour (H₂O) and heat. The electric circuit is used to do work, such as power a motor.

Hydrogen fuel cells produce little noise during operation because they convert chemical energy directly into electrical energy through an electrochemical process, rather than relying on the combustion and gas expansion cycles characteristic of internal-combustion engines.1

Unlike engines that burn fuel to generate mechanical work, fuel cells operate without the noisy, repetitive explosions or moving parts associated with traditional heat engines. This fundamental difference in energy conversion allows them to function quietly, making them a favorable option for applications such as local municipal power-generation stations.1