If a sound is shriekier, it is higher and louder, like a scream.
Shriekier sounds can make people feel scared or surprised.
Examples:
Her voice is shriekier than his.
The cat made a shriekier noise than the dog.
The shriekier the noise, the scarier it is.
I don't like the shriekier sounds, they hurt my ears.
The monster's shriekier roar echoed through the forest.
The siren's shriekier wail made everyone cover their ears.