2. radio lobe sound disk  t p ~ km  optical light cone The Vision *) see e.g. A. Ringwald,ARENA 2005 Build ~100 km 3 hybrid detector to: Confirm GZK cutoff ! Do physics with extremely high energy cosmic neutrinos *) - astrophysics - E > 10 16 eV : study origin of cosmic rays - (AGN’s, black holes, GZK cutoff, …) - particle physics - E > 10 18 eV : study neutrino cross section (sphalerons, mini BH, strong,…) - cosmology - E > 10 21 eV : study relic neutrino background radiation ( UHE absorption at CBR )

3. Acoustic R&D in IceCube 2002 2003 2004 2005 2006 2007 startdevelopment of glaciophones test in lab and at accelerators calibration of sensors and transmitters construction and test of SPATS First SPATS deployment First SPATS results Improvement (S/N) ib = 50 (S/N) gb = 15 In-situ test starts hybrid detector simulation

4. The South Pole Acoustic Test Setup SPATS 3 strings deployed Jan/07 +1 string deployed Dec/07 instrumented depth: 80m - 500m per string: 7 sensors, 7 transmitters string-PC: digitization, time-stamp, monitoring (p, T) master-PC: process steering, GPS data storage data transfer via satellite

5. The Four SPATS Goals Get information about: 1.) Sound speed: what is the sound speed value? is it depth dependent (= refraction ?) 2.) Transient events: are there transients events? what are their features (rate, sources)? could they be a significant source of background ? 3.) Noise: what is the noise level? which energy threshold does it correspond to? 4.) Attenuation coefficient: never measured up to know, only models are known is it depth dependent? is it frequency dependent? Needs time information Needs amplitude information

6. Sound Speed Results bbb paper submitted to Astroparticle Physics First observation of shear waves in SP ice ! v p (375 m) = 3878 ± 12 m/s v S (375 m) = 1976 ± 8 m/s

7. Absolute Noise Level Result - Gaussian - Stable - ≤15 mPa

8. RW07/08 RW06/07 AM-RW RW05/06 - more than one year continous data taking - no surface noise detected - hear 4 steady sources and at least 8 drill holes during re-freezing - x-y resolution depends on depth and location with respect to detector typically better than 10 m - no noise from unknown sources with present trigger conditions Transient Noise Events

9. Energy from the time domain Use pinger data 47 independent measurements (from 49 combinations available) Weighted mean value and error: α = 3.21+/- 0.56 10 -3 m  λ ~ 312+/- 64 m No significant depth dependence No significant frequency dependence up to 30 kHz 1 example channel xxx

10. SPATS Status Summary Mission accomplished to ~95% : - 1) Speed of Sound + Refraction speed of sound constant below 200 m no refraction - 2) Sound Attenuation Length  λ = 300+/- 100 m, factor 30 smaller than expected  still to measure: frequency and depth dependence  possible explanation: larger influence of scattering - 3) Absolute Noise Level gaussian and stable ≤ 10 mPa ( with reasonable assumptions) - 4) Transient Signal Rate small and until now all from identified sources easy to separate from neutrino signal +++ ++ +++ --