Hearing differences in a Stereo Speaker & the Human Voice

[shaunnutley]

I've noticed that i can hear a man's voice at 70dB and at a distance of 50ft with a pair of ear muffs on, but i cannot hear one stereo speaker at the same volume from the same distance away. Why is this the case? The ear muffs i used are the best in the world, Optime III and the sounds were measured from a distance of 1 foot. The speaker has a power of 5 Watts. Both speaker and man had the same voice frequency. What single speaker specifications (watts, speaker size) are the equivalent of a person's voice regardless of the volume? The speaker needs to be a point source, so it does not reduce the sound attenuation over the 50ft.

[meredith101]

there are lots of other variables.
the sound volume dissipates as a function of the distance from the source.
which part of the wave phase you happen to intercept with your ear also has an effect, since part of the auditory system is tuned solely to pick that up.

[wildwood]

Maybe it has something to do with the sound waves from a human traveling in a circle from the source bouncing from surrounding objects whereas from a speaker it is directional. It would be interesting to see the results if you were to repeat your experiment in an empty field.

[mibn2cweus]

As an experiment you might try playing a high quality recording of the same human voice through the speaker. This should at least narrow the range of potential differences between the two sound sources and allow you to narrow down the possible causes of the observed inequity.

I suspect that it may have something to do with the inherent variations in the properties of the two different types of sound, such as dynamic range and frequency bandwidth variations between the sounds as well as pulse versus continuous sound energy yielding similar output readings by the meter while have different perceptual qualities.

[mibn2cweus]

Now having read the rest of your question:

A point source attenuates more quickly than would a broader sound source.

A speaker rarely exceeds an efficiency of 5% in converting input power to acoustic energy with efficiencies of 1% or less being typical.

In terms of power provided by an amplifier rated at 5 watts, this is often very close to a maximum whereas a medium complex audio signal peaking at 5 watts would on average only be at about 1/2 watt or less between peaks. Pushing the amplifier beyond this range wound introduce distortion of the sound increasing as you increase the volume and drive the amplifier to deliver more power to the speaker.