The phrase "where he noticed" is correct and usable in written English.
It can be used to indicate a location where someone noticed something, such as in the following sentence: He was walking down the street when he noticed a sign advertising a sale at the local store.
He went to a nearby Marriott hotel, where he noticed big tables that were draped to the floor.
SCOTTISH legend has it that Robert the Bruce once took shelter in a cave, where he noticed a spider repeatedly trying, and failing, to build a web.
Mr. Kim got the inspiration for the C1 traveling around Asia, where he noticed that many people travel exclusively on motorcycles.
They took him home to a rural village where he noticed that many people had nothing to light their homes, schools and clinics at night.
This year, oak samples were submitted to the Cornell diagnostic clinic by an arborist who was working on a client's trees on private land, where he noticed a few oaks were having problems.
While scouting for an actress who could speak the local dialect, Jia visited a dance class at the Taiyuan Teachers College, where he noticed a tough-minded instructor, Zhao Tao, who came from a steel-mill family.
She refuses to come out, but Harry Dawes, a down-on-his-luck writer and director (Humphrey Bogart), barges into her dressing room, where he notices her bare feet below a drawn curtain; she is embracing her lover.
Jangled by that failing relationship, Woodcock dashes off to his country home and takes breakfast the next morning at a small-town café, where he notices a clumsy young waitress whose bearing catches his attention.
Picasso is with his friend Paul Eluard at the Café des Deux Magots, where he notices Dora at a neighbouring table, "the young woman's serious face, lit up by pale blue eyes which looked all the paler because of her thick eyebrows; a sensitive uneasy face, with light and shade passing alternately over it.
Through this distraction he finds himself within a church, where he notices an old man, Ilia Murin, with his young wife, Katerina.
He goes to the police station, where he notices that Sandy's father's partner is the Yellow Man an officer named Lieutenant Detective Tom Gordon Fred Picklerr).
