Window sound ratings: compare STC and OITC without promising silence

Questions covered in this guide

Describe the noise you want to change

Before shopping for quieter windows, note the room, the sound and the time it bothers you. Is it a passing truck at night, nearby conversation or a regular equipment hum? Add whether the window was closed and what activity was interrupted. This brief record gives a bidder a concrete problem to discuss instead of an undefined request for soundproof glass.

Read matching ratings

Pella's technical manual distinguishes Sound Transmission Class, or STC, from Outdoor–Indoor Transmission Class, or OITC. OITC includes lower-frequency exterior noise. The manual cautions that a rating does not guarantee the same reduction for a particular sound in use. Compare STC with STC and OITC with OITC. Keep these as product-comparison measures rather than promises about your bedroom.

Tie the number to the actual proposal

For each opening, request the product series, operating style, glass configuration, tested size and relevant acoustic report. Ask the bidder to point to the configuration being quoted. Record the standard option and the proposed upgrade in adjacent columns; do not substitute a brand's best advertised rating for the ordered window. Pella also identifies installation and airtight seals as part of sound performance. Ask how the installer will assess the opening and whether other sound paths need investigation. If the concern remains unclear, ask whether an acoustics professional should evaluate it before you commit to a major replacement.

Compare the added scope and price

Keep a row for the upgrade's installed price, rooms included and unanswered performance questions. Request an explanation of what the seller expects the upgrade to address, and what it cannot establish from the available information. The window calculator can use a price supplied for your replacement specification; its general range does not estimate an acoustic package. Save that budget beside your noise record and proposal so the decision remains tied to the problem you actually want solved.

Putting it into practice

A room-and-time noise record is connected to product-specific test data and a separate upgrade price. Matching STC/OITC columns prevent cross-metric comparisons; unanswered sound-path questions remain explicit instead of converting ratings into room guarantees.

Sources and supported claims

Pella distinguishes STC from OITC and explains that OITC includes lower-frequency exterior noise.
Source ↗ · national · Checked 2026-10-12

Pella cautions that an acoustic rating does not guarantee an equal reduction for a particular sound in actual use.
Source ↗ · national · Checked 2026-10-12

Pella identifies proper installation and airtight seals as contributors to sound performance.
Source ↗ · national · Checked 2026-10-12