1. ~ km sound disk p t radio lobe The Vision Build ~100 km3 hybrid detector to: Confirm GZK cutoff ! Do physics with extremelyhigh energy cosmic neutrinos*) - astrophysics - E > 1016eV : study origin of cosmic rays - (AGN’s, black holes, GZK cutoff, …) - particle physics - E > 1018eV : study neutrino cross section (sphalerons, mini BH, strong,…) - cosmology - E > 1021eV : study relic neutrino background radiation (UHE absorption at CBR ) nm optical light cone m *) see e.g. A. Ringwald ,ARENA 2005

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

3. SPATS The South Pole Acoustic Test Setup 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

4. 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 amplitudeinformation

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

6. Absolute Noise Level Result • - Gaussian- Stable- ≤15 mPa

7. Transient Noise Events RW07/08 RW06/07 • 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 detectortypically better than 10 m • no noise from unknown sources with present trigger conditions AM-RW RW05/06

8. Energy from the time domain 1 example channel • 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 xxx

9. 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 +++ -- ++ +++