Aldehydes are readily identified by spectroscopic methods. Using IR spectroscopy, they display a strong "ν"CO band near 1700 cm−1. In their 1H NMR spectra, the formyl hydrogen center absorbs near "δ"H 9.5 to 10, which is a distinctive part of the spectrum. This signal shows the characteristic coupling to any protons on the α carbon with a small coupling constant typically less than 3.0 Hz. The 13C NMR spectra of aldehydes and ketones gives a suppressed (weak) but distinctive signal at "δ"C 190 to 205.