This question comes from someone who loves listening to hard rock music. He said that he likes to put on Black Sabbath, AC/DC and others and really crank it up so even my neighbors can hear. His wive is concerned about the impact on their young daughter and their unborn child. His rationale is that he has ended up okay so it can't be bad for you.
I can't believe I will use this analogy from my past but it applies here. As my mother use to say, if all of your friends jumped off the Brooklyn Bridge would you jump off also? What I would say is if 10 people jumped off, what is the survival rate and what is the individual outcomes. The rationale that because one person turned out normal is not an acceptable rationale. What are the percentages? Next is what do we know about the impacts of this music on the developing child and the unborn child. I am sorry to say that both are not what he will want to hear. Best to leave the music to occasional times when either the family is not around or as a special, lets be crazy and dance to daddy's old music. Also turn it down a notch as you are impacting everyone's hearing.
Fact: Hard rock music increases the release of cortisol which is a stress hormone in both mothers and in unborn infants. Children who are exposed to high levels of cortisol have a greater level of behavior problems and managing emotions as young children and young adults. In other words your children will pay for your choices and you will pay as more difficult parenting situations will arise.