We present the re-scaled vibrational resonance (VR) method and the twice sampling VR method to improve the amplitude-modulated signal. Two different kinds of signals are considered. One is the amplitude-modulated harmonic signal. The other is the amplitude-modulated aperiodic binary signal. Both the VR methods have an excellent effect on the signal improvement. For the re-scaled VR method, the scale parameter is the key factor to determine the resonance output. For the twice sampling VR method, the frequency reduced ratio or the minimal random pulse width stretched ratio is the crucial factor. By choosing appropriate key factors, the output can achieve the strongest resonance and lead to the optimal signal improvement.