The phrase "voice their protest" is correct and can be used in written English.
You can use it when referring to people speaking up about something they disagree with or are unhappy about. For example: After the new mayor's policy was announced, many citizens voiced their protest against it.
They said, in effect, 'Anyone but you!' Those who voted wished primarily to voice their protest against this reform, against this conduct of our government.
Various political, social and religious organizations had announced that they would convene in Genoa to use the occasion of a three-day summit meeting to voice their protest.
Pensioners, students disillusioned by an education system that leads nowhere, nurses exasperated by the lack of resources: all have gathered to voice their protest.
The same crowd that stood on principle for Pat Buchanan's right to draw votes from Bush now frantically accuses Nader of hypocrisy, egomania and unforgivable spoilerism for daring to offer voters a chance to voice their protest.
It could become another protracted and messy affair similar to the one which dragged on earlier in the year when Cellino first attempted to buy the West Yorkshire club, thinking he had completed the deal on a bizarre night in the club's history as fans descended on Elland Road to voice their protest, only to be told later the transaction had not been not ratified.
Taking cue from the scene in which the protagonists hold a silent, candlelight vigil at New Delhi's India Gate, one such group of demonstrators carried out a similar rally to voice their protest.
House members voiced their protest before and after testimony on the second day of hearings of the Oversight and Investigations Subcommittee, part of the House Committee on Energy and Commerce.
The issue caused a storm on Twitter, where people voiced their protest on behalf of vegans, vegetarians and some religious groups.
The trial of Islamists in state security courts for expressing their support for IS on social media has prompted critics to stop voicing their protest on the street as well as the internet.
Many film-makers, activists, politicians have already voiced their protest against this politically motivated process, but it didn't stop the Russian court from issuing an outrageous sentence on 25 August.
Two of France's top art experts have voiced their protest over the cleaning of The Virgin and Child with Saint Anne – a jewel of western art – by resigning from the Paris museum's advisory committee responsible for its "restoration", the Guardian has learned.
