The idea of having a low frequency horn in a sleeping area is to wake up a person, even an older or hard of hearing person, when there's a fire. In a Live/Work Studio, the sleeping area is less well defined than in a regular one- or two-bedroom apartment. From the tenant's point of view, the bed could be out in the open area of the Studio.
The AHJ (Authority Having Jurisdiction) considers that the whole Studio Apartment is the bedroom. If there's a fire, no matter where the bed is placed in the bedroom, the person having the authority over fire safety wants the sound in the entire sleeping area to be able to wake up a person.
Keep in mind that the NFPA 72 Code doesn't define any occupancy (what a space in a building is being used for) as a sleeping area. The NFPA 72 Code only says that if an area's occupancy is defined as a sleeping area, certain requirements are needed for the fire alarms.
The occupancy (what an area is being used for) is defined by the NFPA 101, or the International Building Code (IBC), or a government agency. Generally, the room (no matter what it's size) is what is considered for the occupancy. Not only that, but if the room has more than one type of occupancy, the official designation for the occupancy is the one that has the highest level of need for fire protection / fire alarm. The requirements for bedrooms are much greater than the requirements for living rooms, so for occupancy purposes, the whole room is considered to be one big bedroom.
As far as the "code" goes, the "code" is actually a set of guidelines published by a non-prophet organization called the National Fire Protection Association. By itself, this set of guidelines is not a set of laws that anyone has to obey. It's the government makes the laws that everyone has to obey, and it's the government that has decided to use the NFPA's guidelines as the government's law.
The government's fire marshal or fire inspector interprets the laws, so in essence, the government's fire marshal or fire inspector (the AHJ) has the final say over what the "code" means.
Bottom line, there will have to be a low frequency horn that covers the whole studio area with the required evacuation sound.