
230 S.E.2d 783 (1977)
STATE of North Carolina
v.
James McKinney JEETER and John Frank Craig.
No. 7626SC536.
Court of Appeals of North Carolina.
January 5, 1977.
Certiorari Denied March 7, 1977.
*784 Atty. Gen. Rufus L. Edmisten by Associate Atty. David S. Crump, Raleigh, for the State.
Asst. Public Defender James Fitzgerald, Charlotte, for defendant appellants.
Certiorari Denied by Supreme Court March 7, 1977.
CLARK, Judge.
The sole issue presented upon appeal is whether the trial court committed reversible error in admitting into evidence, over the general objection of the defendant, the entire tape recording made by Sheriff Stahl.
The recorded statements of the three witnesses who testified for the State were offered for the purpose of corroborating their testimony at trial. We find that those prior recorded statements were generally consistent with their trial testimony and that admission was justified in view of the prolonged cross-examination of these witnesses by the defendants relative to the *785 identity of the various participants who forced the victim to participate in homosexual acts per anus and per os. Under these circumstances, and in light of the instructions to the jury limiting the evidence to corroboration if the jury in fact found that it did corroborate, we find that these tape recorded statements of the State's witnesses were admissible for corroboration. 1 Stansbury, N.C. Evidence § 52 (Brandis Rev.1973).
The tape recorded statement of the unidentified "Rudolph", who did not testify at trial, was not admissible for the purpose of corroboration. Apparently, the State had no knowledge that this statement was on the tape which was offered in evidence. It appears from the record that the District Attorney offered in evidence only the recorded statements of the witnesses who had testified for the State.
To be admissible for any purpose a tape recording must be audible and must have been properly authenticated. State v. Lynch, 279 N.C. 1, 181 S.E.2d 561 (1971); State v. Strickland, 276 N.C. 253, 173 S.E.2d 129 (1970); Levi v. Justice and Searcy v. Justice, 27 N.C.App. 511, 219 S.E.2d 518 (1975), petition for discretionary review denied, 289 N.C. 298, 222 S.E.2d 698 (1976). The trial court after voir dire hearing made no findings, but Sheriff Stahl testified that he recorded the conversations on a recording machine which was operating properly; that no changes or deletions had been made in the recorded tape; and that the tape had been in his custody since made. He also identified the voices. Though it is the better practice for the trial judge to make findings relative to authenticity and audibility, where the State's evidence supports both and defendant offers no conflicting evidence, the admission of the tape recording in evidence without such findings of fact is harmless error. See State v. Sharratt, 29 N.C.App. 199, 223 S.E.2d 906 (1976).
In State v. Lynch, supra, the court stated: "Upon an objection to the introduction of a recorded statement, in order to ascertain if it meets the foregoing requirements, the trial judge must necessarily conduct a voir dire and listen to the recording in the absence of the jury. . . This procedure affords counsel the opportunity to object to any portions of the recording which he deems incompetent and permits incompetent matter to be kept from the jury in some appropriate manner." 279 N.C. at 17, 181 S.E.2d at 571.
In the case before us the record does not disclose that the defendants made an objection prior to voir dire. Defendants at no time during voir dire requested that the tape recording be played so that the court and parties could listen. Nor does it appear that when the tape recording was admitted in evidence and played in open court before the jury, the defendants made any objection or motion to stop playing the recorded statement of Rudolph. Nor did defendants move to strike that portion of the recording. Nor did defendants ascertain the contents of the tape recording by discovery under G.S. 15A-903(d), which was enacted subsequent to Lynch and which specifically allows the inspection of electronic recordings.
We find that the inadmissibility of this evidence was waived by the defendants' failure to make a timely objection when they had had the opportunity to learn that the evidence was objectionable. State v. Cook, 280 N.C. 642, 187 S.E.2d 104 (1972); State v. Edwards, 274 N.C. 431, 163 S.E.2d 767 (1968). If inadmissibility is not indicated by the question but becomes apparent by some feature of the answer, a motion to strike should be made as soon as the inadmissibility becomes known. 1 Stansbury, supra, § 27. "Invited error is not ground for a new trial." State v. Payne, 280 N.C. 170, 171, 185 S.E.2d 101, 102 (1971).
Further, in view of the strength of the State's evidence, which included the testimony of the victim and two apparently disinterested eyewitnesses that was corroborated by prior recorded statements, the admission of Rudolph's recorded statement was not prejudicial and did not affect the outcome of the trial. The error, if any, was *786 harmless. See Annot., 58 A.L.R.2d 1024 § 8 (1958).
No error.
MORRIS and ARNOLD, JJ., concur.
