Noise insulation, Engineer types opinions needed Options

[nivekdodge]

Just a thought

There's another thread today discussing using perlon for the back pad and if it was quieter or not. Something I've notice is Some GM hood have their inner surface looking like a golf ball. There are 3" round divots and when asked about it I was told it reflects the sound back to the motor and that kills the sound.Anyone know if there is truth to this?

This would of course be in the engine compartment.

Kevin

[r_towle]

You can attack the firewall problem but in the end the rear window will become the loudest transference of noise.

I think the OEM engine bay rubber pad glued to insulation gave pretty decent results.
I might suggest adding dynamite to the interior of the firewall in addition to the oem engine bay pad, then call it quits.

Rich

[Bucci]

You can attack the firewall problem but in the end the rear window will become the loudest transference of noise.

I think the OEM engine bay rubber pad glued to insulation gave pretty decent results.
I might suggest adding dynamite to the interior of the firewall in addition to the oem engine bay pad, then call it quits.

Rich

Good morning Rich, I did a dual glaze rear window on my 914 almost 30 years ago. Look at the picture below, the identification on the glass is mirrored or doubled.

In fact, right after I put in the 3.2 L motor I ran without a back window for almost a year. Rain does not get into the car when you’re going forward. Lol

[Superhawk996]

You can attack the firewall problem but in the end the rear window will become the loudest transference of noise.

I think the OEM engine bay rubber pad glued to insulation gave pretty decent results.
I might suggest adding dynamite to the interior of the firewall in addition to the oem engine bay pad, then call it quits.

Rich

Good morning Rich, I did a dual glaze rear window on my 914 almost 30 years ago. Look at the picture below, the identification on the glass is mirrored or doubled.

In fact, right after I put in the 3.2 L motor I ran without a back window for almost a year. Rain does not get into the car when you’re going forward. Lol

Creative - I didn’t realize you can fit two layers of glass in there. How did you secure the second pane of glass?

Modern luxury cars often use thicker and sometimes laminated glass on side and rear windows as a way to reduce NVH. The lamination layer acts like constrained layer damping impeding sound transfer from one pane of glass to the other.

[Bucci]

You can attack the firewall problem but in the end the rear window will become the loudest transference of noise.

I think the OEM engine bay rubber pad glued to insulation gave pretty decent results.
I might suggest adding dynamite to the interior of the firewall in addition to the oem engine bay pad, then call it quits.

Rich

Good morning Rich, I did a dual glaze rear window on my 914 almost 30 years ago. Look at the picture below, the identification on the glass is mirrored or doubled.

In fact, right after I put in the 3.2 L motor I ran without a back window for almost a year. Rain does not get into the car when you’re going forward. Lol

Creative - I didn’t realize you can fit two layers of glass in there. How did you secure the second pane of glass?

Modern luxury cars often use thicker and sometimes laminated glass on side and rear windows as a way to reduce NVH. The lamination layer acts like constrained layer damping impeding sound transfer from one pane of glass to the other.

Yes, you can fit two pieces of glass in the space behind the seatbelt anchor point vinyl interior trim. I used balsa wood as an intermediate gasket piece between the glass, (it allowed minor ventilation, so condensation does not fog up the dual glaze window) I then sandwiched the two pieces of glass together with silicone.

@vitamin914

By the way, I did get the idea after looking at a Mercedes sedan that had dual glazed driver and passenger side windows..!