### ASA 125th Meeting Ottawa 1993 May

## 1pSA10. Conditions of existing negative components in instantaneous
frequency analysis.

**Jeung T. Kim
**

**
Byungduk Lim
**

**
**
*Acoust. and Vib. Lab., Korea Res. Inst. of Standards and Sci., P.O. Box 3,
Daedok Science Town, Daejon, Korea 305-606
*

*
*
An instantaneous frequency analysis is a technique to examine a signature
for the rotating machinery if the signal has several transitions within a
cycle. This paper discusses the conditions of existing negative frequency
components in the instantaneous frequency. By using a simple signal that
consists of two frequency components, the instantaneous frequency analysis is
conducted while the amplitude ratio between two frequency components has been
changed. The calculation shows that, depending on the amplitude ratio, the
instantaneous frequencies have averaged, zero-valued, or negative components.
It turns out that the negative-valued instantaneous frequencies, which have
been regarded as the noise effect, are the consequence of the calculation
process for the multisignal components. The criteria to show the condition of
the negative values in instantaneous frequencies is given in terms of the
relative amplitude ratio and the frequency difference. In this paper, a
vibration signal monitored from a rotating machinery is also examined as an
application example in order to show the existence of negative instantaneous
frequencies components.