My cat started going into heat around 6 months of age (January).. Her first couple heat cycles were horendous, kept everyone up all night long.. But as time has gone on, her "help" and "whyyyyyy" sounds are not as intense and abnoxious.
anyways, i haven't really done anything to shut her up, when she starts getting loud, i hold her at the scruff and push down on her with my thumb and index finger on each side where her tail meets with her body. She starts making funny noises, and growls sometimes, but my vet assured me that it wasn't hurting her. (She doesnt like anyone touching her lower back/tailbone, or her tail to begin with) But I try to do this for about 2 minutes (if possible) and once i let go, she just lays down on her side super relaxed and seems like she's out of pain.. It's only temporary though, 2-3 hours she shuts up for.. if she's really being a grouchy pants, she will shut up for about an hour or two.