Exceptional points (${\mathrm{EP}}_{\mathrm{S}}$) can enhance sensitivity for weak signal detection, but noise typically degrades their performance. Here, contrary to this conventional wisdom, we theoretically introduce and experimentally demonstrate a noise-assisted sensing paradigm leveraging stochastic resonances near a driven-dissipative nonlinear fourth-order exceptional point (${\mathrm{EP}}_4$). Using a minimal two-site model with asymmetric dissipation and single-site driving, we realize an ${\mathrm{EP}}_4$ exhibiting fourfold degeneracy in steady-state eigenamplitudes under fixed-frequency driving. Crucially, this ${\mathrm{EP}}_4$ coexists with third-order ${\mathrm{EP}}_{\mathrm{S}}$ and second-order exceptional lines, partitioning a two-parameter space into mono-, bi-, and tristable regions. We demonstrate that noise induces bi- and multistable stochastic resonances, synergizing with the quartic-root dispersion around ${\mathrm{EP}}_4$ to dramatically amplify weak signals and enhance signal-to-noise ratios. Experimental validation with nonlinear electrical circuits confirms these predictions. Our work establishes driven-dissipative nonlinear higher-order ${\mathrm{EP}}_{\mathrm{S}}$ with eigenamplitude degeneracy as a potent platform for noise-enhanced sensing, harnessing nonlinear multistability and EP physics to transcend conventional noise limitations.

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• Noise
• Exceptional points
• Non-Hermitian systems
• Nonlinear waves