Human pitch discrimination is frequency dependent. There is a concept of critical bands. You can read about it in a text on Physics and music by Rigden. I keep promoting that text because I've taught out of it as several universities. There are probably many good texts on the subject. In short, there is a critical minimum frequency difference at which people will not likely be able to hear the difference between two tones. This also has an impact on the perception of consonance and dissonance in an interval. It is a fact that small intervals will be "muddy", more dissonant, and perhaps indistinguishable at low frequencies (in the low registers). That doesn't mean you can't do it. At the end of the day you need to be happy with your arrangement. If you're just looking to arrange a piece of music and trying to find work for each section I'd adhere to the rule (guide line) but it you're composing you have freedom to break the rules. It will produce an effect and as long as that effect is what you want it works. But I'd be careful and try it our during a rehearsal in an auditorium and see if it sounds the way you think it does. The "muddiness" has nothing to do with acoustics and acoustic scattering and interference will make the effect worse. If you find yourself with limited options for notes in lower registers you can always rearrange a piece to have different harmony, chord inversion etc.

Human pitch discrimination is frequency dependent. There is a concept of critical bands. You can read about it in a text on Physics and music by Rigden. I keep promoting that text because I've taught out of it as several universities. There are probably many good texts on the subject. In short, there is a critical minimum frequency difference at which people will not likely be able to hear the difference between two tones. This also has an impact on the perception of consonance and dissonance in an interval. It is a fact that small intervals will be "muddy", more dissonant, and perhaps indistinguishable at low frequencies (in the low registers). That doesn't mean you can't do it. At the end of the day you need to be happy with your arrangement. If you're just looking to arrange a piece of music and trying to find work for each section I'd adhere to the rule (guide line) but it you're composing you have freedom to break the rules. It will produce an effect and as long as that effect is what you want it works. But I'd be careful and try it out during a rehearsal in an auditorium and see if it sounds the way you think it does. The "muddiness" has nothing to do with acoustics and acoustic scattering and interference will make the effect worse. If you find yourself with limited options for notes in lower registers you can always rearrange a piece to have different harmony, chord inversion etc.