SNOW SOUNDS

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Submitted on 1 Jan 1987

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SNOW SOUNDS

P. Camp

To cite this version:

P. Camp. SNOW SOUNDS. Journal de Physique Colloques, 1987, 48 (C1), pp.C1-239-C1-241.

�10.1051/jphyscol:1987133�. �jpa-00226279�

JOURNAL DE PHYSIQUE

Colloque C1, suppl6ment au n o 3, Tome 48, mars 1987

SNOW SOUNDS

P.R. CAMP

University of Maine, Orono, ME 04469, U.S.A.

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Resume.- L y s o n s p r o d u i t s en marchant dans l a neige o n t

6t6

11s sont compares a des sons analogues p r o d u i t s dans du sable.

Abstract.- The sounds made by walking i n snow have been recorded, displayed and s p e c t r a l l y analyzed f o r several snow c o n d i t i o n s . They a r e compared t o s i m i l a r sounds created i n sand.

The c h a r a c t e r i s t i c crunch made when one walks i n snow has o f t e n been remarked [l] and i t has been "explained" as associated w i t h t h e r e l a x a t i o n process o f one g r a i n s l i p p i n g on another [2] t h e " s t i c k - s l i p " process [3]. A modest l i t e r a t u r e search having y i e l d e d l i t t l e f u r t h e r i n f o r m a t i o n , I have recorded a number o f such sounds and analyzed t h e i r spectra. The r e s u l t s c o n f i r m t h e r e l a x a t i o n nature o f the process and show t h a t the sounds created depend on temperature, snow depth and t h e n a t u r e o f t h e m o t i o n c r e a t i n g them.

The sounds were recorded on a p o r t a b l e Sony c a s s e t t e tape r e c o r d e r w i t h t h e microphone h e l d c l o s e t o my boot as I walked i n snow. They were then d i s p l a y e d on an o s c i l l o s c o p e and analyzed on a Data P r e c i s i o n model 6000 F a s t F o u r i e r Transform Analyzer

.

Figure 1A shows t h e o s c i l l o s c o p e t r a c e f o r a t y p i c a l step i n snow a t - 1 7 ' ~ f o r a depth o f 2cm on a hard surface. The r e l a x a t i o n c h a r a c t e r o f t h e process i s e v i d e n t . F i g u r e 1B shows a step i n deep snow, 20cm, a t t h e same temperature.

Figures 2A and 28 show t h e spectra r e s p e c t i v e l y f o r f i g u r e s 1A and 1B. The frequencies below 500Hz are r e l a t i v e l y s t r o n g e r f o r t h e deep snow. (Because o f automatic g a i n c o n t r o l i n t h e system, o n l y t h e r e l a t i v e amplitudes w i t h i n a t r a c e a r e s i g n i f i c a n t . ) F i g u r e 2C shows t h e way i n which t h e n a t u r e o f t h e step can change t h e spectrum. I n t h i s case t h e f o o t was t w i s t e d and t h e h i g h frequencies were much emphasized.

At h i g h temperatures, t h e spectra a r e q u i t e d i f f e r e n t . F i g u r e 3A shows t h e spectrum o f a s t e p i n somewhat corned snow a t -2.5O~ and a depth o f 3cm. The n o i s e i s almost "white". On t h e o t h e r hand, a step i n 3cm o f new snow (good snowball snow) a t - l ° C shows s t r o n g low-frequency components, F i g u r e 38. This i s even more s t r i k i n g i n F i g u r e 3C which shows t h e spectrum f o r t h e same snow b u t on a heavy plank i n s t e a d o f a plowed gravel driveway f o r a s u b s t r a t e .

For comparison w i t h o t h e r sounds, F i g u r e 4A shows the spectrum f o r walking i n 5cm o f d r y Ottowa sand. Although t h e absolute sound l e v e l i s much lower, t h e spectra1 d i s t r i b u t i o n i s somewhat s i m i l a r t o t h a t o f F i g u r e 3B. It i s i n t e r e s t i n g t h a t s l i g h t dampening o f t h e sand ( F i g u r e 4B) causes a l a r g e change i n the spectrum and t h a t f u r t h e r w e t t i n g causes l i t t l e change.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1987133

C1-240 JOURNAL DE PHYSIQUE

I am g r a t e f u l t o Professor Charles Smith, Dr. Paul Dolan and David Craig f o r t h e i r h e l p i n using t h e i r FFT Analyzer.

REFERENCES

[I] Walker, J e a r l , The F l y i n g C i r c u s of P h y s i c s , (John Wiley and Sons, 1 9 7 5 ) , p.5.

[ Z ] Humphreys, W. J.

,

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[3] B r i s t o n , J. R., Proc. Roy. Sco. Lon. A 189, (1947) 88.

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cr B

t-

0.0 0.2 0.4 1000 2000

SECONDS HERTZ

F i g . 1 O s c i l l o s c o p e t r a c e o f s t e p F i g . 2 F.F.T., s t e p s i n snow, i n snow, -170C, A. D e p t h 2cm; A. D e p t h 2cm; 6. D e p t h 20cm;

8. D e p t h 20cm. C. F o o t t w i s t i n g a f t e r s t e p .

HERTZ

F i g . 3 F . F . T . , s t e p s i n snow A . somewhat c o r n e d snow, 3cm d e p t h , - 2 . 5 o c ;

B. new snow, 3cm d e p t h , - l . o ° C ; C . same as B b u t on wood p l a n k .

1000 2000

HERTZ

F i g . 4 F . F . T . , s t e p s i n Ottowa sand, 5cm d e p t h . A . D r y ;

B. S l i g h t l y m o i s t e n e d .