A Sonic Wave-Neutralizer is a Kryptonian portable device that creates Ultra-High and Ultra-Low Frequencies. It was successfully used by Superman against Siryn's UHF/ULF voice that allows to canceling out her "sonic charm" to manipulate people.
The Neutralizer is always carried by Superman to negate Siryn's UHF/ULF voice from interfering in his response to distress calls. When Siryn enrolled in the Xavier Institute, X-Men and later members of the Justice League are equipped with Neutralizers to ensure from being taken advantage.