Have you searched the web for something like soundproofing studio walls?

I imagine there is lots of info available.

Having a hard time getting a good cost estimate

There are 3 methods for reducing the transfer of sound from one space to another:: mass, residency and absorption. You should use all 3 if possible within the limitation of your space and budget. Insulation (absorption) is important but the least effective method. It sort of picks up what the other methods miss.

Mass is the most effective but heavy wall materials like concrete are expensive. Resiliency involves wall materials with a flexible layer that allows the materials to vibrate with the sound and transfer less of it. Materials are resilient channels, channels on resilient clips, acoustic drywall and Green Glue.

Without knowing the space, how it is enclosed, the nature of unwanted sounds, number of people involved, and the budget, its not possible to offer an effective solution. Focus on defining the problem, then find a solution, then get prices.

Be aware that isolating a studio from exterior sound and controlling the sound you make are separate issues.

You have two issues to address. The first is outside noise interfering with your recording. This is what RES is talking about, above. It involves preventing transmission of noises from outside the studio room. Here, things like insulation, isolation, and sealing doors/outlets/etc. are helpful

The other issue is that of sound bouncing around the inside of the studio. To improve the sound quality of your recordings, you'll want to use some acoustic panels.

https://musiccritic.com/equipment/studio/best-acoustic-foam-panels/

https://incomeschool.com/sound-proof-podcast-room/

Mark: I thought that was part of the charm of a podcast, that they sounded like they were broadcast from someone's bedroom or bathroom.

Not here. I don't listen a second time if that's what they sound like.

This book is all you need! https://www.amazon.com/Handbook-Sound-Studio-Construction-Recording-dp-007177274X/dp/007177274X/ref=mt_paperback?_encoding=UTF8&me=&qid=1566054356

For recording voice its not that complicated. The critical information is how noisy the office environment is but we don't have that information so there's not much to discuss..

Thanks, all . This is helpful. Our office is relatively quiet. Our biggest concerns are avoiding the HVAC sounds and tinny sound of voices bouncing off walls, as well as some general chatter or office noise from outside the recording space.

Do you want to modify an existing room or build a new one? Would there be windows in it? What are the floor and ceiling materials? What are the doors like?

Softening the sounds inside the space requires soft materials like carpets and acoustic panels like rigid fiberglass insulation on homasote covered with cloth. Exposed foam is a fire hazard.

@HU-83039429, glad if you could let us know what was the final solution and how did it go.