This might have been a groundbreaking study in 1970, but suffice it to say, we've probably come a bit further than that in the last 45 years. 45 years can mean a lot when it comes to technology and our ability to make use of it for scientific analysis, never mind the wealth of knowledge garnered and built upon in that timeframe. These days we wouldn't just generically say "microphone" - as I mentioned above, the type and model of microphone used matters, as does the preamp, and how much gain was on the signal from the preamp. I'd also venture to guess that "about 5 cm away" and "about one bell radius away" probably wouldn't suffice for any analysis done today - the exact placement of the microphone - the distance and whether the microphone was on or off axis would definitely be considered. With certain mics, being slightly off axis significantly colors the sound, so there would have to be some consistency to that. I think that the one thing that would tickle my fancy with this would be whether or not we could scientifically prove whether or not certain brands of horns with claims to having more core of a sound, or claims to having more overtones present in the sound, are actually true. However, at the end of the day, it still boils down to the who it is behind the horn in the first place, as well as the context when it comes to the musical aspect.