Neither you nor someone else are / is required to cooperate with the police and, if you or someone else chooses to do so, then that choice is made at your or someone else's potential peril. Rest assured that it (your cooperation) will be a one way street, their way (not yours or someone else's), and neither you nor someone else will enjoy any right or privilege - except that of having your cooperation used against you in one way or another. (Just because the voice stress test - a nonsense / BS alleged "science" - is inadmissible in court does not mean that the police cannot use it against you - or someone else - in some other fashion, such as when calculating probable cause.)
It is almost never a good idea to cooperate with law enforcement without having a skilled and experienced criminal defense lawyer at your side, looking out for your interests and protecting you from those who's duty it is to "serve and protect". The cops want to make arrests and close cases. You, or someone else, can easily help them along their way if you do not have a criminal defense lawyer at your side.
I hope that I have been helpful in answering your question.
First, second and third: No attorney-client relationship exists by virtue of any Q&A with Michael A. Haber, Esq. on Avvo. Fourth: Anything that you post on Avvo (or on similar sites) or on any social media is by its nature public. It is essentially an admission / confession and can be introduced into evidence as a statement against your interest in a subsequent legal proceeding. Once posted you lose any reasonable expectation of privacy, so, as this is an open forum (with no privilege attached), please be extra careful when considering what to post online (forewarned is forearmed.)