let out a shrill voice

[Ashiuhto]

Would anyone be kind enough to check the following paragraph for me? Thanks a lot.
Last Saturday, Emily, Mike and I went hiking in the mountains. As we were on our way to the destination, Mike suddenly let out a shrill voice and said, “Look, everybody！ It must be a UFO”. Emily and I were both frightened to see a disc shaped flying object moving fast high up in the sky. It was glittering and the reflections of light coming from within the clouds. We were alarmed at first but soon composed ourselves. We concentrated our attentions on the UFO, and Mike took out his camera to take a picture. However, the disc shaped craft submerged back into the clouds and then disappeared. What a pity!

[Academic Writing]

Would anyone be kind enough to check the following paragraph for me? Thanks a lot.
Mike suddenly let out a shrill voice and said, “Look, everybody!

I would probably say "Mike shouted in a shrill voice, 'Look everybody!'" I think this works well because "said" doesn't really fit with your exclamation point.

Also, because the words are shouted I think the idea of "suddenly" is implicit, although you could include the word for emphasis ("Mike suddenly shouted in a shrill voice...").

You might even be able to say "Mike screeched, 'Look everybody!'" because screech means to shout or cry out in a shrill voice.

If you are writing for a test, I'd probably use one of my options above or something similar. If you are writing your own work of fiction, you'll probably have more creative latitude. (Please note that my usage of single and double quotation marks is standard in U.S. English, but if you are writing in British English, they would be inverted. Also, in your writing, you would only be using one pair of quotation marks, so in that case, just use double quotation marks for the speech if you are writing in U.S English and single quotation marks if you are writing in British English.)

[BobK]

Another option would be 'Mike suddenly let out a shrill cry...'. One doesn't 'let out' a voice of any kind.

b