Internal door types and soundproofing

I live in a 3 bedroom 1950s semi. At the moment the internal doors are a hollow, moulded, four panel type. If you're in a bedroom and have the door shut you can still hear enough to understand a conversation going on in the living room which also has its door shut. Is replacing the doors with solid wooded ones likely to make a difference to how well the sound travels? If so is using oak likely to be any better than a well fitted pine door?

Sound resonates in lots of different ways and mainly from hard surfaces. Whilst a solid door may help, it wouldn't eliminate it. Soft furnishings such as heavy curtains, carpets and underlays would have more effect.

When its feasible, insulation under floors, blue soundproofing plasterboards to ceilings etc but clearly not a very viable solution unless the property was being refurbished or newly built.

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