Ms. Decibel originated from a wealthy British family, where she sought out her dream of being a musical prodigy, particularly trumpet playing. When given her big chance, she was booed for her horrible performance. During said performance, however, the trumpet became (seemingly permanently) wedged inside her trunk. However, the tones emitted through her entrapped instrument had a hypnotic effect on her audience. This prompted Ms. Decibel to seek a life of crime, effortlessly taking control over anyone in her path.
Sly 4: Thieves in Time
Ms. Decibel is first seen as she walks with Le Paradox with Sly eavesdropping on their conversation so that he can pick up on the locations of his ancestor Salim Al Kupar's remaining associate thieves. Posing as a delivery boy acting on Ms. Decibel's behalf, Sly and his gang make their way to the three locations where Salim's associate thieves are locked away. It is revealed that Ms. Decibel has utilized phonograph recordings of her trumpet's tones in order to hypnotize the associate thieves into doing her bidding. Needless to say, Sly and his allies save the associate thieves from this fate.
After planting a bug in her office, they learn that Ms. Decibel is forging documents so as to create a fake royal ancestry for Le Paradox to further his status in the present day. She also has a base which is used to house Le Paradox's blimp, which is naturally infiltrated by The Cooper Gang. Le Paradox, however, moves to escape with the documents and kidnaps Carmelita in the process. Determined to win Le Paradox's good favor, Decibel attacks Sly using shockwaves and energy blasts emitted from her trumpet. Using the Thief costume of the period, Sly is able to slow time enough to successfully dodge her attacks and traverse her energy railings. Towards the end, Decibel tries to attack directly by charging but is defeated after being tricked into crashing against three transmitter towers.
In prison, Decibel seems to have reformed as revealed in the epilogue. She has the trumpet removed and attempts to give music lessons to her fellow prisoners.
Ms. Decibel shows many traits of a stereotypical sophisticated British woman, such as a distinct love for classical music and a disgust with anything unsightly. This extends to her becoming enraged when Bentley distracts her from her office with rock music, which "offends her ears", so as to plant the bug. Ms. Decibel also demonstrates a cultured sense in how her office is filled with countless books and classical documentation- although much of that could also be contributing to her research and work in forging the fake royalty documents for Le Paradox.
Ms. Decibel's main motivation for helping Le Paradox stems from her growing attraction to the skunk, seeing him as a benefactor and potential lover. Le Paradox naturally exploits this to get Decibel to work on his behalf and quite cruelly dismisses her when she attempts to escape with him on his blimp. Until that point, she seems quite determined to win his good favor.
Ms. Decibel's hairstyle is the same as that of Cruella de Vil, perhaps as an intentional shout out given their status as wealthy British criminals.