In this contribution, a novel wireless sensor network (WSN) assisted by $M$-ary frequency-shift keying (MFSK) modulation and frequency-hopping (FH), referred to as the FH/MFSK WSN, is proposed to monitor multiple source events (SEs). In the FH/MFSK WSN, the multiple SEs of each with multiple states are observed by a common group of local sensors (LSNs), each of which observes simultaneously all the SEs. The LSNs convey their decisions through wireless channels to the fusion center (FC) with the aid of MFSK and FH. At the FC, the SEs' states are detected using noncoherent fusion rules. In this contribution, two noncoherent fusion rules are investigated. The first one is the equal gain combining (EGC) fusion rule, while the second one uses both the EGC and iterative interference cancellation (IIC), which is referred to as the EGC-IIC fusion rule. The detection performance of the FH/MFSK WSN employing the proposed EGC or EGC-IIC fusion rule is investigated, when assuming the wireless channels experience independent Rayleigh fading. Our studies show that the FH/MFSK WSN may constitute one of the promising WSN schemes for some special application scenarios. It is capable of monitoring simultaneously multiple SEs of each with multiple states, is low-complexity owing to using the noncoherent fusion rule and, furthermore, is capable of achieving promising detection performance, as it can make use of the diversity in both frequency and space domains.