Low-frequency/long-wavelength density turbulence is found to be reduced withinthe volume enclosed by an electron thermal internal transport barrier generated with lower hybrid microwave heating in the JET tokamak. Theturbulence reduction coincides with a region (typically r/a<0.4) ofnegative, or reversed magnetic shear s and reduced electron thermal diffusionχe. In the tokamak edge region (r/a>0.8), the turbulenceamplitude is also reduced coinciding with large positive magnetic shears>1. Estimates of the core turbulence wavelengths (λ⊥>0.1 m) are not in agreement with expectations from electron temperaturegradient instabilities.