And the winner is air duct. Far left driver side small piece of plastic broke off and vibrated as airflow/speed increased. Thanks for responses.

Thanks, folks! Been laid up, will report back when this round is over.

Thank you for replying. Only while driving, seems to be triggered by higher revs/speed (~50 mph) but occasionally buzzes in low speed traffic. First time was a real hoot. Seems to be in upper part--not sure left or right, perhaps more likely left--of instrument cluster.

1998 V70XC sounds like high revving electrical motor revving behind dash, perhaps triggered intermittently by 50+mph speed. ??? Thanks.