Toyota Previa 2.0D noisy turbo

[UVB]

Hoping someone might be able to point me in the right direction on this one. Mother in law has recently got the above car and the turbo is very noisy. At around 1500rpm it sounds like a police siren is nearby. Above 2000rpm that noise goes away but it is replaced by a very whiny turbo noise that you can hear clearly louder than the engine itself. I've had a variety of turbo cars in the past and none has sounded anywhere near this loud. There's no smoke coming from the back either on startup, revs or overrun. Other than the noise, it seems to run just fine.