Re: Physics of the sound of footsteps (Axel Roebel )

Subject: Re: Physics of the sound of footsteps
From:    Axel Roebel  <Axel.Roebel@xxxxxxxx>
Date:    Wed, 22 Jan 2014 10:43:37 +0100

On 21/01/2014 17:45, Linda Seltzer wrote: > When we walk, we can hear our footsteps, even if we are walking barefoot > on a soft surface. However, the number of steps per second in walking is > below the auditory range. What is it about the impact with the ground > that causes the auditory signal? Are there papers on the acoustics of a > footstep? > > Thank you for any information. We usually perceive each footstep individually, so there is no relation to the number of steps per second and the fact that you hear the footsteps. You would hear a single footstep similar as you hear a single knock on the door. If due to physical conditions you don't hear a single footstep, you wont here the sequence either. Related to the second part of your question. I am not aware of any papers on physics of footsteps, probably because the physical explanation depends on the material that you step on. In general there are multiple events emitting sound related to a single footstep (that's why individual footsteps are probably best treated as a randomly distributed superposition of micro events) E.g. gravel stones move and collide if you step on them. Soft material may make noise when compressed due to air circulating within the material, or due to the fact that the material structure makes sound if deformed, moreover you may have effects that parts of the skin of the foot attaches and detaches form the surface, finally the foot may rub the surface (like you move your hand over a table surface), and you may also hear noise due to air moving when you put your foot and small cavities may form between your skin and the surface where the air is first compressed and then finally evades (This last point is probably the one that makes the least sound in general but it is a potential sound source). So the hypothesis would be if you walk with a perfectly dry feet on a rigid (no deformation) and very smooth (no noise generated by friction) surface (a mirror) then you would not hear your footsteps. Best Axel > Linda Seltzer > -- Axel Roebel Analysis/Synthesis Team, IRCAM Phone: ++33-1-4478 4845 | Fax: ++33-1-4478 1540

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