# Why can we hear instruments but not voices?

I've seen this graph:

But I don't get something. Consider the 2kHz line (highlighted in red).

This graph implies we can hear an orchestral instrument at 2kHz before we can hear a human at the same frequency? But why is that? I would assume we're considering the same amplitude of source, so it doesn't seem like that's the cause.

So if they're the same amplitude and same frequency, they must be the same wave then. Thus how can they be perceived differently?

What's so special about musical instruments that makes them able to be heard earlier?

• The answers are saying this graph describes the min and max that a voice and orchestra can produce. But that doesn't make sense either. A voice should be able to produce a sound quieter than an orchestra or than most instruments. And certainly quieter than 40 db in the mid range. Commented Apr 23, 2022 at 2:51
• That diagram is very uninformative. The acoustic output of orchestral instruments is generally in the range below (roughly) 2 kHz. Trained singers (trained to perform with orchestras) have a vocal quality called the singer's formant. With well developed singers formant capability: the sound production in the vocal system is such that most of the acoustic output is higher harmonics of the ground note; most of the acoustic output is around the 3 kHz range. The audience can hear the singer well, even with the orchestra playing loud Commented Apr 23, 2022 at 6:30
• @mmesser314, Try singing a note as quietly as possible. I think you will find that there is a certain threshold below which the sound you are making abruptly changes from a musical note to a whisper. My guess is that the graph comes from some music curriculum or literature, and that "vocal range" refers specifically to singing. Commented Apr 23, 2022 at 13:00

What’s the source of that graph? I’m guessing that the two inner loops correspond to which sounds can be produced, not which can be heard.

If you look at the graph, you will see that the green area depicts the entire "auditory experience". In other words, anything in that area will be experienced as sound. Outside that, you may either not hear it at all (when very soft, or very high frequency), or you may feel it rather than hear it (at very low frequency, or at very high intensity, which causes pain). And of course, if it is loud enough, you won't hear it because it has destroyed your hearing.

Inside that green area you see smaller areas that show the ranges of sounds that can be produced by an orchestra and by the human voice. Voice has a smaller range than an orchestra, both in frequency and in volume. Hence its area is smaller.

However, both voice and orchestra are within the auditory experience range, and hence audible.

I would assume we're considering the same amplitude

The vertical axis is the sound pressure level. In other words, the vertical axis is the amplitude.

So if they're the same amplitude and same frequency, they must be the same wave then. Thus how can they be perceived differently?

They are not the same amplitude. The graph says that there are orchestral instruments that can produce sounds with smaller or larger amplitudes than the human vocal range