Answer:
False
Step-by-step explanation:
The observers will detect different frequencies based whether the source is approaching them or receding from them. Based on the location of observer, the source may either approach the observer or recede from the observer.
If the source is receding

if the source is approaching

For example, consider a scenario where an ambulance moves from west to east.
There are two observers one located west of the ambulance and other located east of the ambulance The ambulance is receding from the west side observer and approaching the east side observer.
The observer west of the ambulance will hear lower pitch and the observer eat of the ambulance will hear higher pitch.